Suicide and mortality related to mental disorder in three Swedish cohorts

Aims: The subject of this thesis is suicide and other premature death related to mental disorder. The overall aim is to provide knowledge to improve prevention strategies. The specific aims are as follows: Study I: To identify predictors of suicide in a cohort with long-term mental disorder. Study II: To analyse mortality by mental health service and psychiatric diagnosis in a cohort with long-term mental disorder. Study III: To investigate the impact of psychiatric morbidity on suicide risk following a suicide attempt. Study IV: To examine familial suicide risks in a total population sample.

Methods: Studies I and II. Adult residents with mental disorder in Stockholm County, Sweden, were identified in 1997. This register (n=12,247) was linked to national registers. Discharges from psychiatric inpatient care during 1990 2000 and deaths during 1997 2000 were identified. Predictors of suicide in the cohort were investigated; standardised mortality ratios were calculated. Study III. Data on all people living in Sweden 1973 82 were linked to national registers. People hospitalised during the period 1973 82 due to attempted suicide were identified. The cohort (n=39,685) consisted of those with a studied psychiatric diagnosis present at index attempt (cases) and those without a psychiatric diagnosis within a year after the suicide attempt (reference subjects). Patients were followed for 21 31 years. Survival curves for suicide were plotted and hazard ratios computed. Study IV. A population-based cohort (n=7,969,645) was created by linkage of Swedish national registers. Persons with death classified as definite or uncertain suicide 1952 2003 were identified (n=83,951). Odds ratios for suicide in relatives of suicide probands were calculated in relation to relatives of controls.

Results: Study I. Predictors of suicide included previous suicide attempt, a history of psychiatric inpatient care, and unmet need of a contact person. Borderline personality disorder was the strongest diagnostic predictor. Study II. Excess mortality was greater among those with a history of psychiatric inpatient care. The number of excess deaths due to natural causes was threefold that due to external causes. Study III. High proportions of suicides in all diagnostic groups took place within one year. The strongest predictors of completed suicide throughout the entire follow-up were schizophrenia and bipolar/unipolar disorder, with up to 39% suicide mortality. Study IV. The risk increase was threefold in full-siblings and twofold in children. The odds ratio for full-siblings was higher than that for maternal half-siblings. Odds ratios for second- and third-degree relatives were similar. Partners of suicide probands had a higher odds ratio than most biological relatives.

Conclusions: Treatment programs for persons with long-term mental disorder should target both physical and mental health. Unmet needs may signal increased suicide risk in persons with mental disorder. Psychiatric case management should focus on more intensive aftercare during the first years after a suicide attempt in patients with bipolar and unipolar disorder or schizophrenia. The findings of Study IV are not entirely consistent with variance by degree of genetic correlation; the study could identify impact of both shared environment and shared genes in familial transmission of suicidal behaviour.

List of scientific papers

I. Tidemalm D, Elofsson S, Stefansson CG, Waern M, Runeson B (2005). "Predictors of suicide in a community-based cohort of individuals with severe mental disorder." Soc Psychiatry Psychiatr Epidemiol 40(8): 595-600. Epub 2005 Aug 16
https://pubmed.ncbi.nlm.nih.gov/16091857

II. Tidemalm D, Waern M, Stefansson CG, Elofsson S, Runeson B (2008). "Excess mortality in persons with severe mental disorder in Sweden: a cohort study of 12 103 individuals with and without contact with psychiatric services." Clin Pract Epidemiol Ment Health 4: 23
https://pubmed.ncbi.nlm.nih.gov/18854034

III. Tidemalm D, Långström N, Lichtenstein P, Runeson B (2008). "Risk of suicide after suicide attempt according to coexisting psychiatric disorder: Swedish cohort study with long term follow-up." BMJ 337: a2205
https://pubmed.ncbi.nlm.nih.gov/19018040

IV. Tidemalm D, Waern M, Carlström E, Runeson B, Långström N (2010). "Familial clustering of suicide risk: a total population study of 7,969,645 individuals." (Manuscript)