Relationships among insomnia, executive function, and suicidal ideation in depressed outpatients: A mediation analysis.

Insomnia is a risk factor for suicide, and both are associated with cognitive problems. However, prior research has not examined insomnia, cognition, and suicidal ideation within one sample. We describe cross-sectional associations among insomnia, psychomotor speed, set shifting, and suicidal ideation in 85 depressed adults. Greater insomnia was associated with slower psychomotor speed, while slower psychomotor speed was associated with a greater level (i.e., elaboration of suicide planning) and intensity of suicidal ideation in the past week. Slower set shifting was associated with a greater level and intensity of suicidal ideation in the past week. Mediation analysis indicated that psychomotor speed and set shifting both had a significant total effect on the intensity of suicidal ideation in the past week; set shifting also had a significant total effect on the sum of intensity and suicidal ideation level in the past week. The level of insomnia explained only small percentages of the total effect of either psychomotor speed or set shifting on the intensity of suicidal ideation and the sum of intensity and suicidal ideation level. The findings in this sample demonstrate significant associations of slower psychomotor speed and set shifting with suicidal ideation, with negligible contribution from insomnia.