The Influence of Planning and Response Inhibition on Cognitive Functioning of Non-Psychotic Unipolar Depressed Suicide Attempters

Depression is one of the main risk factors for suicide. However, little is known about the intricate relationships among depressive symptomatology in unipolar depression, suicide risk, and the characteristics of executive dysfunction in depressed patients. We compared 20 non-psychotic unipolar depressed suicide attempters to 20 matching depressed non-attempters and to 20 healthy controls to further investigate the possible differences in neuropsychological performance. Depressed subjects were controlled for current suicidal ideation, and their neuropsychological profile was assessed using a range of measures of executive functioning, attention, verbal memory, processing speed, and psychomotor speed. Depressed groups were outperformed by healthy controls. Depressed attempters presented more cognitive impairment than depressed non-attempters on a simple Go/No-go response inhibition task and performed better than non-attempters on the Tower of London planning task. Depressed attempters were clearly distinguished by a deficit in response inhibition (Go/No-go commission errors). The normative planning performance (Tower of London extra moves) of the suicide attempters was unexpected, and this unanticipated finding calls for further research. Normative planning may indicate an increased risk of suicidal behavior.