In the article the problem of compliance to treatment is discussed considering pharmacodynamics of different classes of psychotropic drugs. Use of antipsychotics is associated with a high risk of non-compliance. Antipsychotics can inhibit the endogenous reward system and decreasing its tone reduce adherence to treatment. Both antidepressants and anxiolytics increase the tone of the reward system. But if for antidepressants an increase in adherence is associated with the activation of the reward system limited by related clinical effects, for anxiolytics high adherence to treatment is associated to the rapid development of specific effect and an indirect increase in the tone of the reward system with an increase general subjective satisfaction with treatment. The tolerance associated with the chronic use of benzodiazepine anxiolytics secondarily worsens the situation leading to the development of pathological addiction.