Substance use linked to poor memory, reasoning in BD

By Mark Cowen

The presence of comorbid substance use disorder (SUD) is associated with significantly poorer visual memory and conceptual reasoning skills in patients with bipolar disorder (BD), US study results show.

Furthermore, the researchers found that BD patients with and without a SUD had significantly poorer cognition in most domains compared with mentally healthy individuals.

"Our results highlight the need of additional screening and monitoring of individuals [with BD] who are at risk of abusing substances, as early identification could provide additional interventions and resources which might mitigate the long term cognitive effects of these conditions," comment David Marshall and team from the University of Michigan in Ann Arbor.

The findings come from a study of 256 euthymic BD patients and 97 age- and verbal intelligence-matched mentally healthy individuals. Of the BD patients, 158 had a lifetime history of SUD.

All of the participants underwent a neuropsychologic test battery from which factor scores were calculated for auditory memory, visual memory, fine motor dexterity, verbal fluency and processing speed, conceptual reasoning and set-shifting, processing speed with interference resolution, inhibitory control, and emotion processing.

Analysis revealed that both groups of BD patients had significantly poorer scores than controls for most of the cognitive factors, except for auditory memory and emotion processing, which showed no significant between-group differences.

Among the BD patients, those with SUD had significantly poorer visual memory and conceptual reasoning and set-shifting than those without, with factor scores of -0.3 versus 0.1 and -0.2 versus 0.2, respectively.

The researchers also found a significant interaction between substance use and depressive symptoms on auditory memory and emotion processing. Specifically, BD patients with current depressive symptoms and SUD had poorer auditory memory and emotion processing than did BD patients with either depression or SUD alone.

Marshall and team conclude in Psychiatry Research: "BD patients with a history of SUD demonstrated worse visual memory and conceptual reasoning skills above and beyond the dysfunction observed in these domains among individuals with BD without SUD, suggesting greater impact on integrative, gestalt-driven processing domains."

They add: "Future research might address longitudinal outcome as a function of BD, SUD, and combined BD/SUD to evaluate neural systems involved in risk for, and effects of, these illnesses."

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