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Original Investigation
July 2017

Association of Late Adolescent Personality With Risk for Subsequent Serious Mental Illness Among Men in a Swedish Nationwide Cohort Study

Author Affiliations
  • 1Division of Psychiatry, University College London, London, England
  • 2Department of Public Health Sciences, Unit of Public Health Epidemiology, Karolinska Institute, Stockholm, Sweden
JAMA Psychiatry. 2017;74(7):703-711. doi:10.1001/jamapsychiatry.2017.0583
Key Points

Question  Are adolescent personality traits (social maturity, mental energy, and emotional stability) associated with the risk for subsequent serious mental illness (bipolar disorder, schizoaffective disorder, schizophrenia, and other nonaffective psychoses)?

Findings  In this nationwide longitudinal cohort study of more than 1 million Swedish men, social maturity, mental energy, and emotional stability had a dose-response association with schizophrenia and other psychotic illnesses. Bipolar disorder had a unique U-shaped association with social maturity (with high and low levels increasing risk).

Meaning  Individuals who develop serious mental illnesses have different patterns of premorbid personality, and genetic architecture for personality traits and serious mental illness may be shared.

Abstract

Importance  Understanding of personality as an independent risk factor for serious mental illness (SMI) remains limited. Recently, overlap between the polygenic basis for specific personality traits and specific SMIs has been identified.

Objective  To determine the association of the adolescent personality domains of social maturity, mental energy, and emotional stability with later diagnosis of SMI.

Design, Setting, and Participants  This longitudinal cohort study enrolled Swedish male military conscripts aged 18 or 19 years from January 1, 1974, through December 31, 1997. The diagnosis of an SMI was extracted from the National Patient Register for all inpatient treatment episodes in Sweden from January 1, 1974, through December 31, 2011. Data were analyzed from May 3 to September 16, 2016.

Exposures  Social maturity, mental energy, and emotional stability assessed at conscription interview.

Main Outcomes and Measures  Inpatient diagnoses of bipolar disorder, schizoaffective disorder, schizophrenia, and other nonaffective psychoses occurring until December 31, 2011.

Results  Of the 1 017 691 men included in the cohort, 4310 developed bipolar disorder; 784, schizoaffective disorder; 4823, schizophrenia; and 5013, other nonaffective psychoses. After adjustment, with use of mean scores as a reference, low social maturity (hazard ratio [HR], 1.61; 95% CI, 1.48-1.74), low mental energy (HR, 1.34; 95% CI, 1.24-1.44), and low emotional stability (HR, 1.51; 95% CI, 1.40-1.63) were inversely associated with schizophrenia in a dose-dependent fashion. Other nonaffective psychoses displayed a similar pattern. Bipolar disorder was associated with high (HR, 1.21; 95% CI, 1.09-1.35) and low (HR, 1.12; 95% CI, 1.01-1.25) social maturity and low emotional stability (HR, 1.62; 95% CI, 1.46-1.78). Schizoaffective disorder was associated with low emotional stability (HR, 1.53; 95% CI, 1.26-1.85).

Conclusions and Relevance  Emotional stability is inversely associated with all SMI. Bipolar disorder has a unique U-shaped association with social maturity. Premorbid personality may reflect subtle changes in cerebral function, may combine with symptoms and other neurocognitive deficits to influence illness presentation, and/or may be owing to shared genetic architecture.

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