Deterministic learning and attempted suicide among older depressed individuals: cognitive assessment using the Wisconsin Card Sorting Task

Background: Late-life suicide is an under-investigated public health problem. Among the putative vulnerabilities for this complex multifactorial behaviour are deficits in cognitive control, an ability to integrate and prioritize multiple cognitive processes in order to flexibly adapt behaviour and meet situational demands. We investigated cognitive control during rule learning in a complex and changing environment in older individuals with suicide attempts of varying lethality.

Method: Ninety-three participants over the age of 60 (30 healthy controls, 29 depressed never suicidal, 20 low-lethality suicide attempters, 14 high-lethality suicide attempters) underwent structured clinical and cognitive assessments. Participants then completed the Wisconsin Card Sorting Test (WCST), a well-studied task of cognitive control during rule learning.

Results: High-lethality attempters demonstrated a pattern of deficits involving poor conceptual reasoning, perseverative errors and total errors. Compared to low-lethality attempters and healthy controls, high-lethality attempters demonstrated poor conceptual reasoning, as well as increased rates of perseverative errors and total errors. Compared to non-suicidal depressed participants, high-lethality attempters also made more conceptual errors.

Conclusion: High-lethality suicide attempts among older people are associated with impaired cognitive control during rule learning as detected by the WCST. Our data suggest that impairment in cognitive control during rule learning may represent a vulnerability distinct from the impulsive diathesis, typically manifesting in young, low-lethality attempters. This vulnerability may contribute to the high incidence of serious or, often, fatal suicidal acts in old age.