The behavioural toxicity of antidepressants: effects on cognition and sexual function.

The cognitive system is structured from sets of schema, patterns of neural activity that allow the assimilation or accommodation of new experiences and so, by a process of consolidation, the gradual development of knowledge and understanding. As well as schema for purely cognitive processes, there are similar structures that enable individuals to deal with sexual behaviour and affectual relationships (e.g. hedonia, self-esteem, personal preferences and body image). In depression, there is a well established disruption of cognitive function that results in anhedonia and a loss of pleasure, including that from sexual activities. Many antidepressants also have a direct pharmacological action on the central nervous system and disrupt cognitive function, so increasing anhedonia and impairing sexual function. Drug actions on cognitive structures, which in turn increase anhedonia and reduce sexual libido, are over and above any direct pharmacological effects on the more overt behavioural activities associated with sex, including orgasm, erectile function, potency and ejaculation. The tricyclic antidepressants, for example, destroy the cognitive structures that are vital to maintain normal libido as well as disturbing overt sexual behaviours. Some selective serotonin reuptake inhibitors (SSRIs; paroxetine and sertraline) are associated with behavioural activation that is also responsible for an impairment of sexual function. However, there are clear differences between the SSRIs, and fluvoxamine (relative to the other SSRIs) has little effect on objective measures of cognition or on cerebral and behavioural components of sexual function.