Drugs and depression

Moderate or severe depression is now one of the most common diseases of our time with a prevalence of nearly 3%. It seems likely that this prevalence has increased as a result of the wider use of drugs which have an effect on the neurotransmitters. Changes in the levels of these neurotransmitters in the central nervous system are thought to be the biochemical basis for the development of at least some depressive illnesses. Drug-induced depressions are more likely to occur in those individuals who are genetically predisposed to depression or who have had a previous depressive illness. Other groups who are particularly susceptible to these effects are the elderly. Many groups of drugs have a primary or secondary action on the central nervous system neurotransmitter function. Some 200 drugs have been claimed to cause depression in certain patients, but only a relatively small number precipitate depressive symptoms with any frequency. Those most commonly implicated are the long-acting antipsychotics, barbiturates, ethanol, oral contraceptives and antihypertensive agents. It is important to remember that some drugs, such as reserpine, cause depression as a side-effect during their therapeutic use whereas others, such as fenfluramine, cause depression mainly when they are withdrawn too rapidly. In those patients presenting with depression, it is important to review the current drug therapy in order to assess the part played by these drugs in the development of the depression. Following this assessment, drug therapy should be adjusted appropriately. However, a distinction must be made between the symptoms of depression, those physiological changes which occur during treatment with a variety of drugs, and the patient's reaction to the disease for which they are being treated.