ANTI-DEPRESSANTS AND COGNITION [ back to What's New ]
Neuropsychologists say that depression so lowers cognitive performance on standard tests (e.g. Wechsler Adult Intelligence Scale) that they may postpone testing until administration of anti-depressants, participation in psychotherapy, or both, have lessened the patient's depression. Is this a coincidental association or a causal association? What is the mechanism behind the relationship between cognitive sharpness and depression? A psychological explanation is that people who are depressed are pre-occupied, less attentive to their surroundings and feel tired and depleted. Is there a bio-chemical or neurobiological explanation for the blunting of intelligence by depression? In the January 15, 1999 edition of the Journal of Neuroscience, it was reported that chronic administration of anti-depressants to rats was found to significantly raise the level of certain enzymes in the nucleus accumbens, an area of the brain associated with the presence or absence of  craving, as well as feelings of "emotional reward" such as pleasure or joy. These particular enzymes play a key role in the the encoding of short term memory and its conversion to long term memory by the hippocampus.  Thus a depressed person has less of a supply of the brain enzymes she needs for the hippocampal activity necessary to build long term memory and achieve new learning. Depression and poor short term memory with deficits in new learning are very common after a TBI. Standard treatment of the depression involves anti-depressant medication. Persons with TBI who reject the idea of taking anti-depressants  because they think such drugs are only for "crazy people" should be aware that anti-depressants may boost their replenish the enzymes  they need to boost flagging short term memory function. Further, depression is not craziness. It is a mood disorder directly caused by brain trauma and also results from conscious awareness of being disabled. It is not a sign of weakness and should not be viewed as a stigma. One note of caution. Many clinicians who prescribe the anti-depressant trazadone, find it helps people sleep, but - unlike other anti-depressants, appears to diminish short term memory, sometimes rather dramatically. This brings to mind the oft repeated dictum that brain functions are so complex there are no one-to-one relationships between specific neurotransmitters and specific acts of cognition.