Psychiatric therapeutics is facing a major crisis that originates from its limited efficacy and dubious scientific credibility. Such a crisis requires a radical change in the paradigm that inspires psychiatric research and clinical practice. The new paradigm should integrate in a meaningful way all of the variables that mediate the aetiology and pathogenesis of psychiatric disorders: biological, psychological, developmental, behavioural and social. The essence of the evolutionary study of human psychology and behaviour is just such an integration. Therefore, evolutionary thinking has great potential to improve the clinical care of psychiatric patients. According to a modern view of medicine, the aims of therapy are not only to lessen symptoms and to reverse the pathogenic mechanisms, but also to restore the congruence between a patient’s functional capacities and the conditions of the environment. Evolutionary thinking suggests replacing symptoms with functional capacities as the primary targets of psychiatric treatment. Most mental disorders are conditions of compromised functional capacities. Therapy should aim at improving patients’ capacities necessary to enact behaviours associated with goal achievement. When treating patients, clinicians should distinguish between symptoms caused by dysfunctional mechanisms and symptoms that are adaptive reactions to environmental situations with negative cost–benefit outcomes.