Methods of evaluation of psychoactive drugs

The classification of psychoactive drugs into minor tranquilizers (i.e. antianxiety drugs) and major tranquilizers (i.e. antidepressants, antimaniacs and antipsychotics) is based on clinical symptom rating scales. The group of symptoms in these scales of anxiety, depression, mania and schizophrenia has a shared phenomenology in the sense that the symptoms can be ordered from less to more severe. The inter-observer agreement when using these scales is adequate as agreement is of 80% or higher. By use of rating scales it has been found in controlled clinical trials that minor psychiatric disorders such as anxiety states without depression have a good outcome of placebo in 60 to 65%. In depressive disorders placebo has a good outcome in 20-45%, but in the elderly depressed patient the placebo effect is poorest (25%). Antidepressants have a good outcome in 60-75%, but in the elderly depressed patients only in 50%. In other words the drug-placebo difference is around 25%. In the major psychiatric disorders such as mania and schizophrenia the drug-placebo difference is around 50%. The use of clinical symptom scales in evaluating side-effects of psychoactive drugs is increasing. However, also non-clinical or laboratory tests have an important role in measuring side-effects, especially in motor skills related to car driving. The use of mentally healthy volunteers in measuring side-effects of major tranquilizers seems inadequate. As yet no biological methods to measure clinical effects of the tranquilizers have been developed for practical use.