Recent reports show alarmingly high rates of suicide in middle-aged men, yet there are few long-term prospective studies that focus on suicidal behaviour in men in this age group.

To prospectively explore associations of potential risk factors at age 18 with suicide and self-harm in middle-aged men.

A population-based Swedish longitudinal cohort study of male conscripts with no history of self-harm at enlistment in 1968–1989 (n = 987 583). Conscription examinations included measures of cognitive performance, stress resilience, psychiatric diagnoses, body mass index (BMI), cardiovascular fitness and muscle strength. Suicides and self-harm at age 45–65 years were identified in the National Hospital Register and Swedish Cause of Death Register. Risks were calculated using Cox proportional hazards models.

Low stress resilience (cause-specific hazard ratio CHR = 2.31, 95% CI 1.95–2.74), low cognitive ability (CHR = 2.01, 95% CI 1.71–2.37) as well as psychiatric disorders and low cardiovascular fitness in late adolescence were associated with increased risk for suicide in middle-aged men. Similar risk estimates were obtained for self-harm. In addition, high and low BMI as well as low muscle strength were associated with increased risk of self-harm. Associations also remained significant after exclusion of men with self-harm before age 45.

This prospective study provides life-course perspective support that psychological and physical characteristics in late adolescence may have long-lasting consequences for suicidal behaviour in middle-aged men, a very large population at heightened risk of suicide.

Studies suggest a role for cardiovascular fitness in the prevention of affective disorders.

To determine whether cardiovascular fitness at age 18 is associated with future risk of serious affective illness.

Population-based Swedish cohort study of male conscripts(n = 1 117 292) born in 1950–1987 with no history of mental illness who were followed for 3–40 years. Data on cardiovascular fitness at conscription were linked with national hospital registers to calculate future risk of depression (requiring in-patient care) and bipolar disorder.

In fully adjusted models low cardiovascular fitness was associated with increased risk for serious depression (hazard ratios (HR)=1.96, 95%, CI 1.71–2.23). No such association could be shown for bipolar disorder (HR=1.11, 95% CI 0.84–1.47).

Lower cardiovascular fitness at age 18 was associated with increased risk of serious depression in adulthood. These results strengthen the theory of a cardiovascular contribution to the aetiology of depression.