Suicidal behaviour in bipolar disorder linked to impulsivity

Severe previous suicidal behaviour in patients with bipolar disorder is associated with impulsivity, as reflected by a tendency towards unplanned responses on an immediate memory task, say US researchers.The researchers investigated the relationship between history of suicidal behaviour and impulsivity in 48 adults with a DSM-IV diagnosis of bipolar disorder recruited from an inpatient clinical research unit or an outpatient clinic.Behavioural laboratory impulsivity was measured using immediate memory/delayed memory tasks derived from the Continuous Performance Test. The Barratt Impulsiveness Scale was used as a self-report assessment of impulsivity.Patients' suicide attempt history was ascertained from their clinical records and through interviews with patients and their significant others.Suicide attempts were reported by eight of 17 men and 16 of 31 women, with attempters more likely than non-attempters to be experiencing mixed states at the time of testing and to have met criteria for alcohol abuse.A history of suicide attempts was associated with a greater probability of impulsive responses on the immediate memory task and a shorter impulsive response latency. There were differences in the same direction for delayed memory task but these were not significant. Similarly, suicide attempters had higher scores on the Barratt Impulsiveness Scale than non-attempters, but the differences were not significant.A history of alcohol abuse, current mixed state, and current pure depressive state tended to be associated with severity of suicide attempt history.The researchers also found that as severity of suicide attempt history increased, frequency of impulsive responses increased and response latency diminished. No significant interactions between clinical variables and severity of suicide attempt history were observed.A logistic regression analysis showed that only immediate memory task commission errors/correct detections and latency to a commission error contributed significantly to suicide attempt severity, while current depressed, mixed or manic state, or history of alcohol abuse did not.The researchers conclude that performance on the immediate memory task may therefore be an objectively measurable characteristic that is related to long-term risk of suicidal behaviour.Reference...