The role of physical and mental multimorbidity in suicidal thoughts and behaviours in a Scottish population cohort study

Physical illness and mental disorders play a significant role in fatal and non-fatal suicidal behaviour. However, there is no clear evidence for the effect of physical and mental illness co-occurrence (multimorbidity) in suicidal ideation and attempts. The aim of the current study was to investigate, whether physical/mental health multimorbidity predicted suicidal thoughts and behaviours as outcomes. Data from the West of Scotland Twenty-07 cohort were analysed. Twenty-07 is a multiple cohort study following people for 20 years, through five waves of data collection. Participants who responded to past-year suicidal thoughts and suicide attempt items were grouped into four distinct health-groups based on having: (1) neither physical nor mental health condition (controls); (2) one or more physical health condition; (3) one or more mental health condition and; (4) multimorbidity. The role of multimorbidity in predicting suicidal ideation and suicide attempts was tested with a generalised estimating equation (GEE) model and odds ratios (ORs) and 95% CIs are presented. Whether the effect of multimorbidity was stronger than either health condition alone was also assessed. Multimorbidity had a significant effect on suicidal thoughts and suicide attempts, compared to the control group, but was not found to increase the risk of either suicide-related outcomes, more than mental illness alone. We identified an effect of physical/mental multimorbidity on risk of suicidal thoughts and suicide attempts. Considering that suicide and related behaviour are rare events, future studies should employ a prospective design on the role of multimorbidity in suicidality, employing larger datasets.