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Clinical mental health researchers may understandably struggle with how to incorporate biological assessments in clinical research. The options are numerous and are described in a vast and complex body of literature. Here we provide guidelines to assist mental health researchers seeking to include biological measures in their studies. Apart from a focus on behavioral outcomes as measured via interviews or questionnaires, we advocate for a focus on biological pathways in clinical trials and epidemiological studies that may help clarify pathophysiology and mechanisms of action, delineate biological subgroups of participants, mediate treatment effects, and inform personalized treatment strategies. With this paper we aim to bridge the gap between clinical and biological mental health research by (1) discussing the clinical relevance, measurement reliability, and feasibility of relevant peripheral biomarkers; (2) addressing five types of biological tissues, namely blood, saliva, urine, stool and hair; and (3) providing information on how to control sources of measurement variability., (© 2024 The Authors. BioEssays published by Wiley Periodicals LLC.)

Mitochondrial dysfunction has been implicated in major depressive disorder (MDD). A measure of mitochondrial respiratory chain (RC) enzymatic activity-the Mitochondrial Health Index (MHI)-has previously been found to correlate with stress and emotional states in caregivers. We here report mitochondrial RC activities, mitochondrial DNA copy number (mtDNAcn), and the composite MHI in unmedicated and somatically healthy subjects with MDD (n = 47) and healthy controls (HC) (n = 11). We also explore, in a subset of the MDD sample (n = 33), whether these markers are associated with response to 8 weeks of SSRI treatment. Mitochondrial RC complexes I, II, IV, citrate synthase (CS), mtDNAcn, and the MHI were assayed in peripheral blood mononuclear cells. Treatment response was defined as >50% decrease on the 25-item Hamilton Depression Rating Scale (HRDS-25). There were no significant differences in MHI or any of the mitochondrial markers between MDD subjects and HCs. Compared to SSRI nonresponders, SSRI responders had significantly higher baseline mitochondrial content markers CS (p = 0.02) and mtDNAcn (p = 0.02), and higher complex I activity (p = 0.01). Complex II activity increased significantly over treatment, irrespective of clinical response (p = 0.03). Complex I activity decreased in responders (n = 9), but increased in nonresponders (n = 18) (group x time interaction, p = 0.02). Absolute treatment-associated change in HDRS-25 scores correlated significantly with change in complex I activity between baseline and week 8 (r = 0.47, p = 0.01). Although mitochondrial markers did not distinguish MDD from controls, they did distinguish SSRI responders from nonresponders. If larger studies validate these mitochondrial differences, they may become useful biomarkers and identify new drug targets.

Post-traumatic stress disorder (PTSD) impacts many veterans and active duty soldiers, but diagnosis can be problematic due to biases in self-disclosure of symptoms, stigma within military populations, and limitations identifying those at risk. Prior studies suggest that PTSD may be a systemic illness, affecting not just the brain, but the entire body. Therefore, disease signals likely span multiple biological domains, including genes, proteins, cells, tissues, and organism-level physiological changes. Identification of these signals could aid in diagnostics, treatment decision-making, and risk evaluation. In the search for PTSD diagnostic biomarkers, we ascertained over one million molecular, cellular, physiological, and clinical features from three cohorts of male veterans. In a discovery cohort of 83 warzone-related PTSD cases and 82 warzone-exposed controls, we identified a set of 343 candidate biomarkers. These candidate biomarkers were selected from an integrated approach using (1) data-driven methods, including Support Vector Machine with Recursive Feature Elimination and other standard or published methodologies, and (2) hypothesis-driven approaches, using previous genetic studies for polygenic risk, or other PTSD-related literature. After reassessment of ~30% of these participants, we refined this set of markers from 343 to 28, based on their performance and ability to track changes in phenotype over time. The final diagnostic panel of 28 features was validated in an independent cohort (26 cases, 26 controls) with good performance (AUC = 0.80, 81% accuracy, 85% sensitivity, and 77% specificity). The identification and validation of this diverse diagnostic panel represents a powerful and novel approach to improve accuracy and reduce bias in diagnosing combat-related PTSD.

BackgroundIncreased inflammation is reported in Major Depressive Disorder (MDD), which may be more pronounced in suicidal subjects. Vitamin D deficiency may drive this pro-inflammatory state due to vitamin D's anti-inflammatory effects.MethodsWe quantified plasma 25-hydroxyvitamin D (25(OH)D) and inflammatory markers interleukin (IL)-6 and tumor necrosis factor (TNF)-α, and other inflammatory indices, neutrophil-to-lymphocyte ratio (NLR) and white blood cell count (WBC) in 48 un-medicated MDD subjects (n = 17 with mild-to-moderate suicidal ideation [SI]) and 54 controls. IL-6 and TNF-α were combined into a composite inflammation score.ResultsThere were no significant differences in 25(OH)D levels between MDD and controls (p = 0.24) or between MDD with and without SI (p = 0.61). However, 25(OH)D was negatively correlated with all measured inflammatory markers; these correlations were stronger in MDD subjects, and particularly in those with SI. MDD status significantly moderated the relationships between 25(OH)D and NLR (p = 0.03), and 25(OH)D and WBC (p

IntroductionCurrent pharmacological treatments of post-traumatic stress disorder (PTSD) have limited efficacy. Although the diagnosis is based on psychopathological criteria, it is frequently accompanied by somatic comorbidities and perhaps "accelerated biological aging," suggesting widespread physical concomitants. Such physiological comorbidities may affect core PTSD symptoms but are rarely the focus of therapeutic trials.MethodsTo elucidate the potential involvement of metabolism, inflammation, and mitochondrial function in PTSD, we integrate findings and mechanistic models from the DOD-sponsored "Systems Biology of PTSD Study" with previous data on these topics.ResultsData implicate inter-linked dysregulations in metabolism, inflammation, mitochondrial function, and perhaps the gut microbiome in PTSD. Several inadequately tested targets of pharmacological intervention are proposed, including insulin sensitizers, lipid regulators, anti-inflammatories, and mitochondrial biogenesis modulators.ConclusionsSystemic pathologies that are intricately involved in brain functioning and behavior may not only contribute to somatic comorbidities in PTSD, but may represent novel targets for treating core psychiatric symptoms.

Aging is associated with complex biological changes that can be accelerated, slowed, or even temporarily reversed by biological and non-biological factors. This article focuses on the link between biological aging, psychological stressors, and mental illness. Rather than comprehensively reviewing this rapidly expanding field, we highlight challenges in this area of research and propose potential strategies to accelerate progress in this field. This effort requires the interaction of scientists across disciplines - including biology, psychiatry, psychology, and epidemiology; and across levels of analysis that emphasize different outcome measures - functional capacity, physiological, cellular, and molecular. Dialogues across disciplines and levels of analysis naturally lead to new opportunities for discovery but also to stimulating challenges. Some important challenges consist of 1) establishing the best objective and predictive biological age indicators or combinations of indicators, 2) identifying the basis for inter-individual differences in the rate of biological aging, and 3) examining to what extent interventions can delay, halt or temporarily reverse aging trajectories. Discovering how psychological states influence biological aging, and vice versa, has the potential to create novel and exciting opportunities for healthcare and possibly yield insights into the fundamental mechanisms that drive human aging.

BackgroundLess than half of patients with major depressive disorder (MDD) respond to their first antidepressant trial. Our understanding of the underlying mechanisms of selective serotonin reuptake inhibitors (SSRIs) remains poor, and there is no reliable method of predicting treatment response.MethodsThirty-seven MDD subjects and 41 healthy controls, somatically healthy and medication-free for at least six weeks, were recruited, and plasma serotonin (5-HT) levels were assessed at baseline. Twenty-six of the MDD subjects were then treated in an open-label manner with clinically appropriate doses of sertraline for 8 weeks, after which plasma 5-HT levels were again assessed. Response to treatment was defined as an improvement of 50% or more on the Hamilton Depression Rating Scale.ResultsNon-responders to sertraline treatment had significantly lower pre-treatment 5-HT levels compared to both healthy controls and responders (F = 4.4, p = 0.004 and p = 0.036, respectively). There was a significant decrease in 5-HT levels over treatment in all MDD subjects (t = 6.2, p = 0.000003). The decrease was significantly more prominent in responders compared to non-responders (t = 2.1, p = 0.047). There was no significant difference in post-treatment 5-HT levels between responders and non-responders.LimitationsThe study had a modest sample size. 5-HT levels in plasma may not reflect 5-HT levels in the brain.ConclusionsThe results indicate that SSRI response may be facilitated by adequate baseline plasma 5-HT content and that successful SSRI treatment is associated with greater decreases in circulating 5-HT. Plasma 5-HT content may be a predictor of SSRI treatment outcome. Potential underlying mechanisms are discussed.

The "neurotrophic hypothesis of depression" posits that low levels of brain-derived neurotrophic factor (BDNF) are associated with Major Depressive Disorder (MDD). Low levels of BDNF have also been found in individuals with suicide attempts, in MDD or other disorders, suggesting that low BDNF may also be associated with suicidality. We assessed serum BDNF in 68 physically healthy and unmedicated (for at least 6 weeks) MDD subjects, who expressed no suicidal ideation (NSI; N = 40) or endorsed suicidal ideation (SI; N = 28), but were not actively suicidal, and in healthy controls (HC; N = 76). Serum BDNF levels were significantly lower in MDD with SI compared to NSI MDD but were not significantly correlated with total Hamilton Depression Rating Scale (HDRS-17) severity or severity on any HDRS subscale. Covarying for age, sex, body mass index, platelets, perceived stress, smoking and physical activity did not alter the significant association between BDNF and SI. SI status was not significantly different between HC and MDD. Our findings show an association between low serum BDNF and SI in individuals with less than severe and non-active suicidal intent, suggesting that the individual symptom of suicidality may extend the neurotrophic hypothesis of depression to include suicidal ideation within MDD.

Telomere attrition is a hallmark of cellular aging and shorter telomeres have been reported in mood and anxiety disorders. Telomere shortening is counteracted by the enzyme telomerase and cellular protection is also provided by the antioxidant enzyme glutathione peroxidase (GPx). Here, telomerase, GPx, and telomeres were investigated in 46 social anxiety disorder (SAD) patients in a within-subject design with repeated measures before and after cognitive behavioral therapy. Treatment outcome was assessed by the Liebowitz Social Anxiety Scale (self-report), administered three times before treatment to control for time and regression artifacts, and posttreatment. Venipunctures were performed twice before treatment, separated by 9 weeks, and once posttreatment. Telomerase activity and telomere length were measured in peripheral blood mononuclear cells and GPx activity in plasma. All patients contributed with complete data. Results showed that social anxiety symptom severity was significantly reduced from pretreatment to posttreatment (Cohen's d = 1.46). There were no significant alterations in telomeres or cellular protection markers before treatment onset. Telomere length and telomerase activity did not change significantly after treatment, but an increase in telomerase over treatment was associated with reduced social anxiety. Also, lower pretreatment telomerase activity predicted subsequent symptom improvement. GPx activity increased significantly during treatment, and increases were significantly associated with symptom improvement. The relationships between symptom improvement and putative protective enzymes remained significant also after controlling for body mass index, sex, duration of SAD, smoking, concurrent psychotropic medication, and the proportion of lymphocytes to monocytes. Thus, indices of cellular protection may be involved in the therapeutic mechanisms of psychological treatment for anxiety.

DNA methylation patterns change with age and can be used to derive an estimate of "epigenetic age," an indicator of biological age. Several studies have shown associations of posttraumatic stress disorder (PTSD) with worse somatic health and early mortality, raising the possibility of accelerated biological aging. This study examined associations between estimated epigenetic age and various variables in 160 male combat-exposed war veterans with (n = 79) and without PTSD (n = 81). DNA methylation was assessed in leukocyte genomic DNA using the Illumina 450K DNA methylation arrays. Epigenetic age was estimated using Horvath's epigenetic clock algorithm and Δage (epigenetic age-chronological age) was calculated. In veterans with PTSD (Δage = 3.2), Δage was on average lower compared to those without PTSD (Δage = 5.0; p = 0.02; Cohen's d = 0.42). This between-group difference was not explained by race/ethnicity, lifestyle factors or childhood trauma. Antidepressant use, however, explained part of the association. In the PTSD positive group, telomerase activity was negatively related to Δage (β = -0.35; p = 0.007). In conclusion, veterans with PTSD had significantly lower epigenetic age profiles than those without PTSD. Further, current antidepressant use and higher telomerase activity were related to relatively less epigenetic aging in veterans with PTSD, speculative of a mechanistic pathway that might attenuate biological aging-related processes in the context of PTSD.

Major depressive disorder (MDD) has been linked to mitochondrial defects, which could manifest in mitochondrial DNA (mtDNA) polymorphisms or mutations. Additionally, copy number of mtDNA (mtDNA-cn) can be quantified in peripheral blood mononuclear cells (PBMC)s, indirectly reflecting cellular energetics, or in the circulating cell-free mtDNA (ccf-mtDNA) levels, which may reflect a fraction of the mitochondrial genome released during cellular stress. Few studies have examined ccf-mtDNA in MDD, and no studies have tested its relationship with intracellular mtDNA-cn or with antidepressant treatment response. Here, mtDNA levels were quantified in parallel from: (i) PBMCs and (ii) cell-free plasma of 50 unmedicated MDD subjects and 55 controls, in parallel with PBMC telomere length (TL) and antioxidant enzyme glutathione peroxidase (GpX) activity. MtDNA measures were repeated in 19 MDD subjects after 8 weeks of open-label SSRI treatment. In analyses adjusted for age, sex, BMI, and smoking, MDD subjects had significantly elevated levels of ccf-mtDNA (F = 20.6, p = 0.00002). PBMC mtDNA-cn did not differ between groups (p > 0.4). In preliminary analyses, we found that changes in ccf-mtDNA with SSRI treatment differed between SSRI responders and non-responders (F = 6.47, p = 0.02), with the non-responders showing an increase in ccf-mtDNA and responders not changing. Baseline ccf-mtDNA was positively correlated with GpX (r = 0.32, p = 0.001), and PBMC mtDNA correlated positively with PBMC TL (r = 0.38, p = 0.0001). These data suggest that plasma ccf-mtDNA and PBMC mtDNA-cn reflect different cellular processes and that the former may be more reflective of certain aspects of MDD pathophysiology and of the response to SSRI antidepressants.

BackgroundAdolescent anxiety and depression are highly prevalent psychiatric disorders that are associated with altered molecular and neurocircuit profiles. Recently, increased mitochondrial DNA copy number (mtDNA-cn) has been found to be associated with several psychopathologies in adults, especially anxiety and depression. The associations between mtDNA-cn and anxiety and depression have not, however, been investigated in adolescents. Moreover, to date there have been no studies examining associations between mtDNA-cn and brain network alterations in mood disorders in any age group.MethodsThe first aim of this study was to compare salivary mtDNA-cn between 49 depressed and/or anxious adolescents and 35 well-matched healthy controls. The second aim of this study was to identify neural correlates of mtDNA-cn derived from diffusion tensor imaging (DTI) and tractography, in the full sample of adolescents.ResultsThere were no diagnosis-specific alterations in mtDNA-cn. However, there was a positive correlation between mtDNA-cn and levels of anxiety, but not depression, in the full sample of adolescents. A subnetwork of connections largely corresponding to the left fronto-occipital fasciculus had significantly lower fractional anisotropy (FA) values in adolescents with higher than median mtDNA-cn.LimitationsUndifferentiated analysis of free and intracellular mtDNA and use of DTI-based tractography represent this study's limitations.ConclusionsThe results of this study help elucidate the relationships between clinical symptoms, molecular changes, and neurocircuitry alterations in adolescents with and without anxiety and depression, and they suggest that increased mtDNA-cn is associated both with increased anxiety symptoms and with decreased fronto-occipital structural connectivity in this population.

BackgroundOxidative stress is implicated in both depression and anxiety, but it is currently unclear whether this relates to syndromal diagnoses or trans-diagnostic dimensional symptoms. We examined the relationship between oxidative stress and severity of depression and anxiety symptoms in individuals with Major Depressive Disorder (MDD).MethodsPlasma oxidative stress markers F2-isoprostanes and oxidized glutathione (GSSG), and the antioxidant reduced glutathione (GSH), were assessed in 69 physically healthy, medication-free MDD subjects. Symptoms of anxiety and depression were assessed using the Hamilton Anxiety (HAM-A) and Hamilton Depression (HAM-D) Rating Scales. Total HAM-A and HAM-D scores, along with "core" anxiety and depression subscales, and individual HAM-D items "psychic anxiety" and "depressed mood," were related to oxidative stress markers. Analyses controlled for age, sex, BMI, and smoking.ResultsTotal HAM-A ratings were positively associated with F2-isoprostanes (β=.26, p=.042) and GSSG (β=.25, p=.049), but not GSH (β=.05, p=.711). Core anxiety severity was positively associated with F2-isoprostanes (β=.34, p=.012) and GSSG, although this did not reach significance (β=.24, p=.074). None of the biological markers were significantly associated with total HAM-D or core depression ratings (all p>.13). Subjects scoring high on "psychic anxiety" had elevated F2-isoprostanes (p=.030) and GSSG (p=.020). This was not seen with "depressed mood" scores (all p>.12).LimitationsWe assessed peripheral oxidative markers, but their relationship to the brain is unclear.ConclusionsOxidative stress is more closely related to anxiety than depression symptoms in MDD. This highlights the importance of relating oxidative stress to specific symptoms and could provide new insights into the biological correlates of affective disorders.

BackgroundDehydroepiandrosterone (DHEA) and its sulfated ester DHEA-sulfate (DHEA-S), (together DHEA[S]), are the most abundant adrenal steroids in humans and are found in blood and the brain, where they function as neurosteroids with direct receptor affinities. Preclinical studies suggest that DHEA(S) has antidepressant/neuroprotective properties, and exogenously administered DHEA has shown antidepressant efficacy in humans. Nonetheless, the role of endogenous DHEA(S) levels in major depressive disorder (MDD) and antidepressant outcomes remains unclear.MethodsMorning fasting serum DHEA(S) concentrations were determined in 36 healthy, unmedicated MDD adults with Hamilton Depression (HDRS) ratings ≥17, and 75 healthy controls. MDD participants then completed eight weeks of open-label SSRI treatment before DHEA(S) levels were re-sampled; those with post-treatment HDRS ratings ≤7 were classified as "Remitters." Pre- and post-treatment DHEA(S) levels of Remitters and Non-remitters were compared, controlling for age, sex, and BMI.ResultsPre-treatment HDRS ratings did not differ between Remitters and Non-remitters (p=0.179). Baseline DHEA levels of Remitters were significantly higher than both Non-remitters (p=0.008) and controls (p=0.004); baseline DHEA-S levels of Remitters were also higher than Non-remitters (p=0.040) but did not significantly differ from controls (p=0.096). Non-remitters did not significantly differ from controls. Post-treatment DHEA(S) levels remained higher in Remitters compared to Non-remitters (DHEA: p=0.013; DHEA-S: p=0.040).ConclusionsThese data suggest that higher circulating DHEA(S) levels (while unmedicated and after eight weeks of SSRI treatment) predict SSRI-associated remission in MDD. This raises the possibility that endogenous DHEA(S) abundance is a physiological adjunct to SSRI efficacy, as suggested by prior preclinical and clinical studies.

ObjectiveIncreased inflammation and oxidative stress have been shown in Major Depressive Disorder (MDD), although there is significant heterogeneity across studies. Whether markers of inflammation and oxidative stress are associated with antidepressant treatment response in MDD is currently unclear. The goals of the present study are to investigate markers of inflammation and oxidative stress in unmedicated MDD subjects and controls and test the relationship between these markers and antidepressant response in MDD subjects.MethodsInterleukin (IL)-6, tumor necrosis factor (TNF)-α, C-reactive protein, F2-isoprostanes, 8-OH 2-deoxyguanosine (8-OHdG), glutathione peroxidase, glutathione, and vitamin C were quantified in blood samples from 50 unmedicated MDD subjects and 55 healthy controls. Depression symptom severity was rated with the 17-item Hamilton Depression Rating Scale (HDRS). All subjects were somatically healthy and free from medications that could interfere with inflammation and oxidative stress markers. A subgroup of 22 MDD subjects underwent open-label selective serotonin reuptake inhibitor (SSRI) antidepressant treatment for eight weeks, after which blood sampling and the HDRS were repeated. Antidepressant treatment "response" was defined as ≥50% decrease in HDRS ratings over 8 weeks of treatment.ResultsAfter controlling for the effects of age, sex, body mass index and smoking, MDD subjects had significantly higher levels of IL-6 (p

ObjectiveThis study examined the relationship between leukocyte telomere length (LTL), a marker of cell aging, and psychiatric disorders in adults compared with controls using meta-analytic methods.MethodsData were abstracted from studies examining the relationship between LTL and adult psychiatric disorders. In addition to an overall estimate of effect size, subgroup analyses and meta-regression were performed to examine whether covariates (including psychiatric diagnoses) moderated the estimate.ResultsA significant overall effect size showing LTL shortening was found across all psychiatric disorders (Hedge g = -0.50, p < .001). Subgroup analyses did not demonstrate significant differences in effect size based on individual covariates (psychiatric disorder, sex, age, or assay method). The meta-regression indicated that although type of disorder and, likely, age moderate the overall effect size, the heterogeneity between studies could not be explained by a model that included these variables as well as sex and assay method. Although not significantly different, posttraumatic stress disorder, anxiety disorders, and depressive disorders had comparatively larger effect sizes (-1.27, -0.53, and -0.55), and psychotic and bipolar disorders had comparatively smaller ones (-0.23 and -0.26).ConclusionsWe observed a robust effect size of LTL shortening for psychiatric disorders as a whole compared with controls. The results were less straightforward regarding relative differences in the strength of this association by specific disorder. Future studies should focus on mechanisms explaining accelerated cell aging with psychiatric illness, defining directions (if any) of causality and elucidating possible differences in this association between disorders.

Short leukocyte telomere length (LTL) may be associated with several psychiatric disorders, including major depressive disorder (MDD). Short LTL has previously been associated with poor response to psychiatric medications in bipolar disorder and schizophrenia, but no studies have prospectively assessed the relationship of LTL to SSRI response in MDD. We assessed pre-treatment LTL, depression severity (using the Hamilton Depression Rating Scale [HDRS]), and self-reported positive and negative affect in 27 healthy, unmedicated adults with MDD. Subjects then underwent open-label treatment with a selective serotonin reuptake inhibitor (SSRI) antidepressant for eight weeks, after which clinical ratings were repeated. Analyses were corrected for age, sex and BMI. "Non-responders" to treatment (HDRS improvement

IntroductionMitochondrial abnormalities may be involved in PTSD, although few studies have examined this. Mitochondrial DNA copy number (mtDNAcn) in blood cells is an emerging systemic index of mitochondrial biogenesis and function. The present study assessed mtDNAcn in male combat-exposed veterans with PTSD compared to those without PTSD as well as its correlation with clinical scales.MethodsmtDNAcn was assessed with a TaqMan multiplex assay in granulocytes of 43 male combat veterans with (n=43) or without (n=44) PTSD. Twenty of the PTSD subjects had co-morbid major depressive disorder (MDD). The Clinician Administered PTSD Scale (CAPS), the Positive and Negative Affect Schedule (PANAS), the Early Trauma Inventory (ETI) and the Beck Depression Inventory II (BDI-II) were used for the clinical assessments. All analyses were corrected for age and BMI.ResultsmtDNAcn was significantly lower in subjects with PTSD (p

BackgroundSeveral psychiatric disorders may be characterized by peripheral telomere shortening. However, it is unclear whether telomere shortening is associated with these psychiatric disorders per se or, rather, with underlying dimensional parameters that are often, but not necessarily, associated with them. We explored the association between dimensional psychopathological measures and telomere length (TL) in granulocytes among veterans independent of psychiatric diagnosis.MethodsSeventy-six combat-exposed male veterans (41 psychiatrically healthy, 18 with Posttraumatic Stress Disorder [PTSD] and 17 with concomitant PTSD and Major Depressive Disorder [MDD]) had TL assayed. Assessments included Clinician-Administered PTSD Scale (CAPS), Beck Depression Inventory-II (BDI-II), Early Trauma Inventory (ETI), Symptom Checklist-90-R Global Severity Index (SCL-90-GSI), Perceived Stress Scale (PSS) and Positive and Negative Affect Schedule (PANAS). Correlations were corrected for age, BMI, antidepressants and ethnicity.ResultsAcross subjects, TL was negatively correlated with early trauma (p

Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell's mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets.

Accelerated cell aging, indexed in peripheral leukocytes by telomere shortness and in peripheral blood mononuclear cells (PBMCs) by telomerase activity, has been reported in several studies of major depressive disorder (MDD). However, the relevance of these peripheral measures for brain indices that are presumably more directly related to MDD pathophysiology is unknown. In this study, we explored the relationship between PBMC telomerase activity and leukocyte telomere length and magnetic resonance imaging-estimated hippocampal volume in un-medicated depressed individuals and healthy controls. We predicted that, to the extent peripheral and central telomerase activity are directly related, PBMC telomerase activity would be positively correlated with hippocampal volume, perhaps due to hippocampal telomerase-associated neurogenesis, neuroprotection or neurotrophic facilitation, and that this effect would be clearer in individuals with increased PBMC telomerase activity, as previously reported in un-medicated MDD. We did not have specific hypotheses regarding the relationship between leukocyte telomere length and hippocampal volume, due to conflicting reports in the published literature. We found, in 25 un-medicated MDD subjects, that PBMC telomerase activity was significantly positively correlated with hippocampal volume; this relationship was not observed in 18 healthy controls. Leukocyte telomere length was not significantly related to hippocampal volume in either group (19 unmedicated MDD subjects and 17 healthy controls). Although the nature of the relationship between peripheral telomerase activity and telomere length and the hippocampus is unclear, these preliminary data are consistent with the possibility that PBMC telomerase activity indexes, and may provide a novel window into, hippocampal neuroprotection and/or neurogenesis in MDD.

Several psychiatric disorders, including major depressive disorder (MDD), are associated with increased blood markers of oxidative stress. The relevance of this to the oxidation-sensitive hippocampus (HC) is unknown. We investigated the relationship between peripheral oxidative stress markers and HC volume in unmedicated individuals with MDD (n=16) and healthy controls (n=19). To conserve power, our primary analysis was carried out in the combined group of subjects, and secondary analyses examined each group separately. Oxidative stress markers (oxidized glutathione (GSSG)) and antioxidants (reduced glutathione (GSH), glutathione peroxidase (Gpx), and Vitamin C) were assessed, and a "total net antioxidant score" was calculated. 4-T MRI estimated total HC volume and HC subfield (CA1, CA1-CA2 transition zone, subiculum and CA3/dentate gyrus [CA3&DG]) volumes. Across groups, the antioxidant score was significantly and positively correlated with total HC volume and CA3&DG subfield volume (normalized to total intracranial volume), adjusting for age and sex. Similar relationships were observed in each individual group but missed statistical significance, likely due to type II errors, with the exception of a significant correlation between the antioxidant score and CA3&DG volume in the MDD group. These preliminary data are consistent with oxidative stress being associated with smaller total HC and CA3&DG subfield volumes.

Background: Several psychiatric disorders may be characterized by peripheral telomere shortening. However, it is unclear whether telomere shortening is associated with these psychiatric disorders per se or, rather, with underlying dimensional parameters that are often, but not necessarily, associated with them. We explored the association between dimensional psychopathological measures and telomere length (TL) in granulocytes among veterans independent of psychiatric diagnosis.Methods: Seventy-six combat-exposed male veterans (41 psychiatrically healthy, 18 with Posttraumatic Stress Disorder [PTSD] and 17 with concomitant PTSD and Major Depressive Disorder [MDD]) had TL assayed. Assessments included Clinician-Administered PTSD Scale (CAPS), Beck Depression Inventory-II (BDI-II), Early Trauma Inventory (ETI), Symptom Checklist-90-R Global Severity Index (SCL-90-GSI), Perceived Stress Scale (PSS) and Positive and Negative Affect Schedule (PANAS). Correlations were corrected for age, BMI, antidepressants and ethnicity.Results: Across subjects, TL was negatively correlated with early trauma (p<0.001), global psychopathological severity (p=0.044) and perceived stress (p=0.019), positively correlated with positive affect (p=0.026), not significantly correlated with symptom severity of PTSD, depression or negative affect. Across these dimensions, early trauma and positive affect were associated with TL after excluding subjects with somatic illnesses.Limitations: The study was cross-sectional with a moderate sample size and only male combat-exposed subjects.Conclusions: These preliminary findings suggest that early trauma, severity of perceived stress and general psychopathological symptoms are more closely associated with shorter TL than is the severity of core diagnostic symptoms of PTSD or MDD, whereas positive affect is associated with longer TL. Larger-scale studies should assess TL associated with specific psychiatric dimensions, apart from only categorical psychiatric diagnoses, to develop more specific biologically-relevant endophenotypes. [ABSTRACT FROM AUTHOR]

Background: Despite several lines of evidence from preclinical and post-mortem studies suggesting that inflammation is involved in Multiple System Atrophy (MSA), no previous studies have measured peripheral indices of inflammation in MSA patients. Methods: We measured C-reactive protein, interleukin (IL)-6, soluble IL-2 receptor and tumor necrosis factor (TNF)-α in blood samples from MSA patients (n = 14) and healthy controls (n = 40). Results: IL-6 and TNF-α were significantly elevated in MSA patients compared to healthy controls. After controlling for the potentially confounding effects of age, gender, and somatic co-morbidities, a diagnosis of MSA was still significantly associated with high levels of TNF-α. Higher TNF-α levels were associated with less severe motor symptoms and earlier disease stage. Conclusions: Our findings are in line with the hypothesis that inflammation might be involved at an early stage of MSA pathophysiology. [ABSTRACT FROM AUTHOR]

• Stress and mental illness are prospectively associated with biological aging. • Technical limitations can compromise the interpretation of biological age indicators. • Integrating biological age indicators into composite indices improves their usefulness. • Human psychobiology is an opportunity to elucidate basic aging processes. • We highlight key challenges and suggest recommendations to overcome them. Aging is associated with complex biological changes that can be accelerated, slowed, or even temporarily reversed by biological and non-biological factors. This article focuses on the link between biological aging, psychological stressors, and mental illness. Rather than comprehensively reviewing this rapidly expanding field, we highlight challenges in this area of research and propose potential strategies to accelerate progress in this field. This effort requires the interaction of scientists across disciplines - including biology, psychiatry, psychology, and epidemiology; and across levels of analysis that emphasize different outcome measures - functional capacity, physiological, cellular, and molecular. Dialogues across disciplines and levels of analysis naturally lead to new opportunities for discovery but also to stimulating challenges. Some important challenges consist of 1) establishing the best objective and predictive biological age indicators or combinations of indicators, 2) identifying the basis for inter-individual differences in the rate of biological aging, and 3) examining to what extent interventions can delay, halt or temporarily reverse aging trajectories. Discovering how psychological states influence biological aging, and vice versa, has the potential to create novel and exciting opportunities for healthcare and possibly yield insights into the fundamental mechanisms that drive human aging. [ABSTRACT FROM AUTHOR]

Posttraumatic stress disorder (PTSD) is associated with increased risk for Type 2 diabetes and cardiovascular disease (cardiometabolic disease), warranting research into targeted prevention strategies. In the present case–control study of 160 young (mean age 32.7 years) male military veterans, we aimed to assess whether PTSD status predicted increased markers of cardiometabolic risk in otherwise healthy individuals, and further, to explore biological pathways between PTSD and these increased markers of cardiometabolic risk. Toward these aims, we compared measures of cardiometabolic risk, namely insulin resistance (IR) (HOMA-IR), metabolic syndrome (MetS) and prediabetes, between 80 PTSD cases and 80 controls without PTSD. We then determined whether PTSD-associated increases in HOMA-IR were correlated with select biological variables from pathways previously hypothesized to link PTSD with cardiometabolic risk, including systemic inflammation (increased C-reactive protein, interleukin-6, and tumor necrosis factor α), sympathetic over-activity (increased resting heart rate), and neuroendocrine dysregulation (increased plasma cortisol or serum brain-derived neurotrophic factor (BDNF)). We found PTSD diagnosis was associated with substantially higher HOMA-IR (cases 4.3 ± 4.3 vs controls 2.4 ± 2.0; p < 0.001), and a higher frequency of MetS (cases 21.3% vs controls 2.5%; p < 0.001), but not prediabetes (cases 20.0% vs controls 18.8%; p > 0.05). Cases also had increased pro-inflammatory cytokines ( p < 0.01), heart rate ( p < 0.001), and BDNF ( p < 0.001), which together predicted increased HOMA-IR (adjusted R 2 = 0.68, p < 0.001). Results show PTSD diagnosis in young male military veterans without cardiometabolic disease is associated with increased IR, predicted by biological alterations previously hypothesized to link PTSD to increased cardiometabolic risk. Findings support further research into early, targeted prevention of cardiometabolic disease in individuals with PTSD. [ABSTRACT FROM AUTHOR]