The WHO Collaborative Study on Psychological Problems in General Health Care examined the frequency, form, course and outcome of psychological problems in general health care settings. A total of 25,916 general health care attenders at 15 sites in 14 countries were screened using the 12-item General Health Questionnaire (GHQ-12). Of those screened, 5,438 were assessed in detail using a Primary Health Care version of the Composite International Diagnostic Interview (CIDI-PHC) in conjunction with the Brief Disability Questionnaire, the Social Disability Schedules, a self rated overall health status form and the 28-item General Health Questionnaire. The analysis has shown that sleep problems were common at all sites with: 26.8% of all patients having some form of sleep problem and 15% of the patients examined had trouble falling or staying asleep. Of those with sleep problems, 51.5% had a well-defined International Classification of Diseases 10th Revision (ICD-10) mental disorder (such as depression, anxiety, somatoform disorders or alcohol problems) and 48.5% of those with sleep problems for at least two weeks or more did not fulfil the criteria for any well defined ICD-10 diagnosis. Persons with sleep problems reported a degree of disability in the performance of their daily activities and social roles even when they had no symptoms of psychological disorders. When such symptoms were present the disability was significantly increased.

The form, frequency and burden of sleep problems in general health care in the WHO Collaborative Study on Psychological Problems are presented in this same issue. This study was conducted in 5,438 primary care patients belonging to 15 centres in 14 countries after 25,916 patients were screened with the GHQ-12. Diagnoses according to the International Classification of Diseases (ICD-10) were obtained from the Composite International Diagnostic Interview (CIDI-PHC). The presence of difficulties falling asleep, staying asleep, waking too early or sleeping too much were assessed by the CIDI. General practitioners (GPs) gave their opinion on the existence of a psychological problem and/or a physical disease and indicated what therapeutic intervention was proposed to patients they recognized as psychological cases. The existence of sleep problems increased the recognition of patients with psychiatric disorders by their GP. No specific subtype of sleep problems influences recognition. The existence of a somatic disease had little influence on the identification of sleep problems as psychological cases. Sleep problems were not frequently expressed as a main presenting complaint. In such a case the recognition rate of patients with ICD-10 diagnosis was unchanged but a sedative treatment was offered more frequently. Overall, 85.9% of patients with sleep problems and recognized as cases were offered treatment, 53.9% drug treatment. The most frequent treatment consumed was stimulants, tonics or vitamins while the most frequently prescribed were antidepressants, hypnotic and anxiolytics with rather similar proportions. Drug consumption was substantially lower than drug prescription.

The difficulty to recruit homogeneous samples of insomniacs requires alternative approaches for sleep studies. Acoustic perturbation in healthy volunteers made it possible to determine an experimental model of acute situational insomnia in order to investigate the effects of classic and novel hypnotic compounds. Unfortunately, the traditional scoring parameters of sleep are inadequate to provide reliable information for defining the neurophysiological bases of insomnia and for evaluating the efficacy of hypnotic drugs. Recent studies on the microstructure of sleep have permitted to identify a specific EEG feature, the cyclic alternating pattern (CAP), correlated with the subjective appreciation of sleep quality. Comparing placebo, zolpidem, zopiclone, lorazepam and triazolam, given at equivalent therapeutic doses in middle-aged healthy volunteer subjects under basal conditions and under acute situational insomnia, provided non-significant information when using classical sleep parameters whereas CAP rate (the percentage ratio of CAP time to non-REM sleep time) permitted to discriminate the basal nights from the perturbed nights and the drug nights from the placebo nights. These data have been confirmed in clinical studies using zolpidem versus placebo in chronic insomniacs.

The purpose of this review was to analyze the literature for potential next-day residual effects of zolpidem, a non-benzodiazepine hypnotic, following nighttime administration. Based on more than 30 international clinical trials involving more than 2,600 subjects/patients, it can be concluded that at the recommended doses of zolpidem 10 mg for adults and zolpidem 5 mg for the elderly, at single or repeated dosing, in healthy subjects or insomniac patients, zolpidem appears to induce minimal next-day residual effects. As for all sedative hypnotics, zolpidem is indicated for the short-term treatment of insomnia and is recommended to be taken only when the patient is able to get a full night's sleep before resuming usual activities.

Different forms of insomnia are present as symptoms of many psychiatric and other disorders. The first step for a treatment strategy is therefore a correct diagnosis. As insomnia is more common in patients with psychiatric disorders than in the general population, a careful consideration should be given, depressive and anxiety disorders should especially be carefully investigated. There are reasons to believe that even in so-called insomnia not obviously related to psychiatric disorders, stressful life situations may play a role. Therefore a co-morbidity with emotional disorders which may follow these events is worth considering. Insomnia should always be considered as pan of a sleep-wake schedule disturbance and this has an impact on the importance of the pharmacological properties of the drugs used to treat insomnia. The recent trend for more specific agents both on receptor sub-populations and on relevant sites of the GABA receptor complex will help very much in selecting the most appropriate drug for treating patients.