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Background: Increasing prevalence of recreational cannabis use among the young population has stimulated debate on the possible effects of acute and longterm use.Aims: To highlight recent knowledge of mechanisms of action, effects on psychomotor and cognitive performance, and health risks associated with cannabis consumption.Method: A brief review of recent literature on the prevalence of recreational cannabis use, the potency of modern cannabis preparations and the pharmacological actions of cannabis.Results: Cannabinoids derived from herbal cannabis interact with endogenous cannabinoid systems in the body. Actions on specific brain receptors cause dose-related impairments of psychomotor performance with implications for car and train driving, aeroplane piloting and academic performance. Other constituents of cannabis smoke carry respiratory and cardiovascular health risks similar to those of tobacco smoke.Conclusions: Cannabis is not, as widely perceived, a harmless drug but poses risks to the individual and to society. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to article about the buspirone in treating mentally ill persons in the November 1990 issue.

A letter to the editor is presented in response to the article about the long-term use of transcutaneous electrical stimulation, published in the May 1992 issue.

Objectives: EEG abnormalities and neurocognitive deficits have been reported in patients with bipolar affective disorder. The aim of this study was to ascertain whether brain function remains impaired in young bipolar patients who have become euthymic in response to treatment., Methods: Brain function was assessed by quantitative electroencephalographic (EEG) power-spectral mapping and by a battery of neuropsychological tests. The subjects were 29 euthymic bipolar patients aged 18-40 years and 26 healthy volunteers of similar age, IQ and socioeconomic status., Results: Grand means of spectral power of the resting EEG showed significantly (from p < 0.01 to p < 0.0001) greater power in all wave bands (delta, theta, alpha and beta) in patients compared with controls. The most marked increases were in right temporal theta and left occipital beta power (with eyes open) encompassing brain areas concerned in visuospatial processing. Neurocognitive performance was significantly impaired in the patients compared with controls in a range of visuospatial tasks., Conclusions: The findings show significant disturbance of EEG activity and deficits in visuospatial processing in young bipolar patients despite clinical euthymia. The abnormalities were not related to age of onset or duration of illness and do not appear to be attributable to medication. The cognitive impairments were associated with the number of previous affective episodes.

Rationale: Abnormalities of cortical evoked potentials and background electroencephalographic (EEG) frequencies occur in several psychiatric disorders, some of which, especially depression, are associated with hypercortisolaemia. However, there have been few investigations of the effects of exogenously administered cortisol on waking EEG measures., Objectives: To examine the effects of subchronic hydrocortisone administration on auditory evoked potentials and background EEG activity., Methods: Hydrocortisone, 20 mg twice daily, or placebo was administered to 30 normal male volunteers for 7 days in a between-subjects, double-blind trial. Auditory evoked potentials and EEG frequencies were measured on the last day., Results: Hydrocortisone significantly increased the amplitudes of the N1P2 and P300 components of the auditory evoked response, but there was no change in background EEG., Conclusion: The results indicate that subchronic hydrocortisone treatment in normal subjects increases the amplitude of auditory evoked potentials, possibly reflecting a central alerting effect.

Background: Previous studies suggest that brain serotonin neurotransmission may mediate the actions of lithium carbonate. Acute tryptophan depletion (ATD) reduces brain serotonin and allows the study of this neurotransmitter in patient groups. Serotonin modulates electroencephalographic (EEG) activity, which is abnormal in bipolar disorder, and EEG abnormalities persist in euthymic bipolar patients. The EEG may therefore be a sensitive marker of 5-HT function in bipolar disorder., Aims: This study examined the effects of ATD on mood, suicidal ideation and EEG activity in bipolar patients who were symptomatically stable on lithium., Methods: 19 subjects satisfying DSM-IV criteria for bipolar I disorder participated in a within-subject, double-blind, placebo-controlled random-order crossover study. Following acute tryptophan depletion (induced by a 100g amino acid drink following an overnight fast) symptoms were evaluated, quantitative power spectrum brain mapping and measurement of auditory evoked potentials were carried out., Results: ATD produced a significant fall in the amplitude of N1P2 and P300 components of the auditory evoked potential, but no significant changes in the power spectrum. There was an 83% reduction in plasma tryptophan (p<0.05, paired t-test) after the depleting but not the control drink. No significant changes in mood or suicidally scores were recorded after ATD., Conclusions: ATD attenuates auditory evoked potentials in bipolar disorder but does not reverse lithium's effects on mood and suicidally in bipolar disorder.