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Children of parents with chronic pain have higher rates of pain and internalizing (eg, anxiety and depressive) symptoms than children of parents without chronic pain. Parental modeling of pain behaviour and reinforcement of child pain have been hypothesized to underlie these relationships. These mechanisms were tested in a sample of 72 parents with chronic pain and their children (aged 8-15 years). Standardized measures were completed by parents (pain characteristics, pain interference, and child internalizing) and children (pain catastrophizing, pain over previous 3 months, and internalizing). In a laboratory session, children completed the cold pressor task in the presence of their parent, and parent-child verbalizations were coded. Significant indirect effects of parental pain interference on child self-reported (B = 0.12, 95% confidence interval [CI]: 0.01-0.29) and parent-reported (B = 0.16, 95% CI: 0.03-0.40) internalizing symptoms through child pain catastrophizing were found (parental modeling mechanism), and were not moderated by child chronic pain status. Significant indirect effects were found between parent pain-attending verbalizations and child self-reported (B = 2.58, 95% CI: 1.03-5.31) and parent-reported (B = 2.18, 95% CI: 0.93-4.27) cold pressor task pain intensity and tolerance (B = -1.02, 95% CI: -1.92 to -0.42) through child pain-attending verbalizations (parental reinforcement mechanism). Although further understanding of the temporal relationships between these variables is needed, the current study identifies constructs (eg, parent pain interference, child pain catastrophizing, and parent reinforcement of child pain) that should be further examined as potential targets for prevention and intervention of pain and internalizing symptoms in children of parents with chronic pain.

Offspring of parents with chronic pain may be at risk for poorer outcomes than offspring of healthy parents. The objective of this research was to provide a comprehensive mixed-methods, systematic synthesis of all available research on outcomes in offspring of parents with chronic pain. A systematic search was conducted for published articles in English examining pain, health, psychological, or family outcomes in offspring of parents with chronic pain. Fifty-nine eligible articles were identified (31 population-based, 25 clinical, 3 qualitative), including offspring from birth to adulthood and parents with varying chronic pain diagnoses (e.g., mixed pain samples, arthritis). Meta-analysis was used to synthesize the results from population-based and clinical studies, while meta-ethnography was used to synthesize the results of qualitative studies. Increased pain complaints were found in offspring of mothers and of fathers with chronic pain, and when both parents had chronic pain. Newborns of mothers with chronic pain were more likely to have adverse birth outcomes, including low birthweight, preterm delivery, caesarean section, intensive care admission, and mortality. Offspring of parents with chronic pain had greater externalizing and internalizing problems and poorer social competence and family outcomes. No significant differences were found on teacher-reported externalizing problems. The meta-ethnography identified six key concepts (developing independence, developing compassion, learning about health and coping, missing out, emotional health, and struggles communicating with parents). Across study designs, offspring of parents with chronic pain had poorer outcomes than other offspring, although the meta-ethnography noted some constructive impact of having a parent with chronic pain.

Catastrophizing is recognized as a key psychosocial factor associated with pain-related negative outcomes in individuals with chronic pain. Longitudinal studies are needed to better understand the temporal relationship between these constructs. The aim of this study was to determine if changes in catastrophizing early in treatment predicted subsequent changes in pain intensity and interference later in treatment, or alternately, if early changes in pain intensity and interference predicted subsequent changes in catastrophizing. A total of 538 patients with neuropathic pain were recruited from 6 multidisciplinary pain clinics across Canada. Study participants were asked to complete measures of catastrophizing, pain intensity, and interference when first seen in the clinic and then again at 3- and 6-month follow-ups. Cross-lagged panel analyses were used to determine the temporal associations among the study variables. The results showed that decreases in catastrophizing early in treatment prospectively predicted improvement in both pain intensity and interference later in treatment. Converse temporal relationships were also found, where a reduction in pain intensity and interference early in treatment predicted a subsequent diminishing of catastrophizing. All 4 unique cross-lagged correlations significantly accounted for an additional 4% to 7% of the total variance. The findings are consistent with theoretical models hypothesizing a causal impact of catastrophizing on pain, suggesting a mutual causation between these factors. The results support that treatments targeting catastrophizing may influence other pain-related outcomes, and conversely that treatments aiming to reduce pain could potentially influence catastrophizing. There may therefore be multiple paths to positive outcomes.

In many countries timely access to care is a growing problem. As medical costs escalate health care resources must be prioritized. In this context there is an increasing need for benchmarks and best practices in wait-time management. The Canadian Pain Society struck a Task Force in December 2005 to identify benchmarks for acceptable wait-times for treatment of chronic pain. As part of the mandate a systematic review of the literature regarding the relationship between waiting times, health status and health outcomes for patients awaiting treatment for chronic pain was undertaken. Twenty-four studies met the inclusion criteria for the review. The current review supports that patients experience a significant deterioration in health related quality of life and psychological well being while waiting for treatment for chronic pain during the 6 months from the time of referral to treatment. It is unknown at what point this deterioration begins as results from the 14 trials involving wait-times of 10 weeks or less yielded mixed results with wait-times amounting to as little as 5 weeks, associated with deterioration. It was concluded that wait-times for chronic pain treatment of 6 months or longer are medically unacceptable. Further study is necessary to determine at what stage the deterioration begins from the onset of pain to treatment and the impact of waiting on treatment outcomes. Most important is the need to improve access to appropriate care for patients with chronic pain, an escalating public health care problem with significant human and economic costs.

Adenosine analogs produce analgesic actions in nociceptive paradigms and alleviate manifestations of neuropathic pain in nerve injury models in rodents. In humans, previous work indicates an analgesic effect for adenosine administered intravenously in postoperative and neuropathic pain. In this double blind placebo controlled crossover trial, we used an enriched enrolment design to determine the effects of intravenous adenosine (50 microg/kg/min over 60min) on neuropathic pain. In Phase 1 of the trial, adenosine was administered in an open label manner, while in Phase 2 adenosine was administered in a double blind placebo controlled manner to 23 adenosine responders who had experienced a 30% or greater response in the open trial. Outcome measures included the McGill pain questionnaire (MPQ), which generates a pain rating index (PRI), and contains a visual analog scale (VAS) of pain intensity, the neuropathy pain scale (NPS), and a VAS for pain relief. Subjects also graded the degree of allodynia and hyperalgesia using a VAS. Adenosine led to a significant reduction in spontaneous pain according to the MPQ-PRI, the MPQ-VAS and the VAS for pain relief. The NPS showed a pattern similar to the MPQ-PRI, with statistically significant reductions in scales 1 (intensity), 3 (hot), 6 (sensitive), 7 (itchy) and 9 (unpleasant). Adenosine also led to a significant reduction in pinprick hyperalgesia, but not in allodynia. Three patients from Phase 1 of the trial experienced long term resolution of their pain following intravenous adenosine (5,16,25 months). The results of this study support previous reports that indicate intravenous adenosine alleviates neuropathic pain and hyperalgesia.

There has been a surge in interest in medicinal cannabis in Canada. We conducted a questionnaire survey to determine the current prevalence of medicinal cannabis use among patients with chronic non-cancer pain, to estimate the dose size and frequency of cannabis use, and to describe the main symptoms for which relief was being sought. Over a 6-week period in mid-2001, 209 chronic non-cancer pain patients were recruited in an anonymous cross-sectional survey. Seventy-two (35%) subjects reported ever having used cannabis. Thirty-two (15%) subjects reported having used cannabis for pain relief (pain users), and 20 (10%) subjects were currently using cannabis for pain relief. Thirty-eight subjects denied using cannabis for pain relief (recreational users). Compared to never users, pain users were significantly younger (P=0.001) and were more likely to be tobacco users (P=0.0001). The largest group of patients using cannabis had pain caused by trauma and/or surgery (51%), and the site of pain was predominantly neck/upper body and myofascial (68% and 65%, respectively). The median duration of pain was similar in both pain users and recreational users (8 vs. 7 years; P=0.7). There was a wide range of amounts and frequency of cannabis use. Of the 32 subjects who used cannabis for pain, 17 (53%) used four puffs or less at each dosing interval, eight (25%) smoked a whole cannabis cigarette (joint) and four (12%) smoked more than one joint. Seven (22%) of these subjects used cannabis more than once daily, five (16%) used it daily, eight (25%) used it weekly and nine (28%) used it rarely. Pain, sleep and mood were most frequently reported as improving with cannabis use, and 'high' and dry mouth were the most commonly reported side effects. We conclude that cannabis use is prevalent among the chronic non-cancer pain population, for a wide range of symptoms, with considerable variability in the amounts used. Discussions between patients and health care providers concerning cannabis use may facilitate education and follow up, and would allow side effects and potential interactions with other medications to be monitored. Clinical trials of cannabis for chronic non-cancer pain are warranted.