New research reveals that lower intelligence and poorer emotional control in adolescence are associated with an increased risk of suicidal thoughts and behaviors over the life course.

However, while lower intelligence is linked to a consistently higher suicide risk into late middle age, the association between emotional control and suicide risk diminishes in strength over time.

Key Facts:

Men with lower intelligence at age 18-20 had a 50% higher suicide risk over 38 years of follow-up. The association remained stable into their late 50s.
Men with poorer emotional control at 18-20 had double the suicide risk over 38 years. But this link weakened considerably with age.
After adjusting for each other, intelligence and emotional control were still associated with suicide risk. But emotional control less so in later life.
Findings suggest value of early intervention for emotional control problems to prevent youth suicide.
Stable link between intelligence and suicide highlights socioeconomic factors as suicide risks into midlife.

Source: Psychol Med. 2020

A large Swedish study published in Psychological Medicine provides new perspective on psychological risk factors for suicidal behaviors over the life span.

Researchers linked intelligence and emotional control data from over 48,000 men around age 18 to national records on suicide attempts and deaths up to age 59.

The decades-long follow-up allowed a unique look at how predictive these adolescent traits are for suicidal thoughts and actions into middle age.

It also gave insight into how the risk associations change over time.

Lower Intelligence & Poorer Emotional Control Linked to Higher Suicide Risk

As expected, the research found that lower intelligence and poorer emotional control at conscription were associated with an elevated risk of suicidal behaviors over the 38-year follow-up period.

Men in the lowest scoring groups on standardized intelligence and emotional control tests had a 6- to 7-fold higher rate of suicide attempts or death by suicide compared to the highest scoring groups.

Modeling intelligence and emotional control as continuous variables, the researchers found:

Each single unit decrease in intelligence score was linked to a 54% higher suicide risk over 38 years.
Each single unit decrease in emotional control score was linked to a 68% higher suicide risk over 38 years.

The findings align with previous studies linking suicidal behaviors to lower intelligence and higher neuroticism.

Neuroticism, involving frequent negative emotions and poor stress control, closely matches the concept of emotional control used here.

Links Change Over Time – Emotional Control Link Weakens with Age

When analyzed over separate decades, a key difference emerged.

While lower intelligence showed a persistent link to higher suicide risk into late middle age:

In the teens and 20s, lower intelligence conferred a 65% higher suicide risk.
In the late 40s and 50s, it still conferred a 53% higher suicide risk.

The connection between poorer emotional control and suicide risk substantially weakened over time:

In the teens and 20s, poorer emotional control conferred a 117% higher suicide risk.
But by the late 40s and 50s, it conferred just a 44% higher suicide risk.

The researchers confirmed that the declining strength of association between emotional control and suicide with age was statistically significant.

Adjusting for Each Other, Emotional Control More Attenuated

The researchers also modeled intelligence and emotional control together, adjusting for each other, to test independence of effects.

Adjusting reduced associations modestly, but did not change the difference in stability of risks over time:

Emotional control was more attenuated, especially in later decades.
But intelligence remained a stable suicide risk factor even adjusted for emotional control.

This implies somewhat independent paths by which lower intelligence and poorer emotional control influence suicide risk over the life course.

Explanations for Changing Risks Over Time

Stable link between intelligence and suicide

The researchers did not expect this persistent connection between lower intelligence and suicide risk.

Since intelligence is generally stable over life, this may highlight downstream socioeconomic factors as steady suicide risks:

Lower intelligence predicts lower education, income, and social status.
These factors are established risks for suicidal behaviors.

Weakening link between emotional control and suicide

In contrast, the weakening link between emotional control and suicide has some explanations:

Emotional control is more variable over life than intelligence.
Neuroticism and poor coping tend to improve starting in the 20s.
Youth suicides may follow acute distress around life events. As resilience improves, this effect fades.

Implications for Suicide Prevention Efforts

Focus on emotional control in youth

The data highlight a high but diminishing suicide risk associated with poor emotional control in young men.

This suggests a need to prioritize access to mental health services and development of coping skills early in life.

Some evidence suggests counseling and therapy can improve neurotic tendencies and build resilience.

Address socioeconomic disadvantages in adulthood

The persistent suicide risk associated with lower intelligence points to chronic socioeconomic disadvantage.

Broader public health initiatives to address inequality may be needed alongside mental health interventions.

More Research Needed in Women and Other Populations

As the study included only Swedish men, further research should investigate whether similar risk patterns occur in:

Women – for whom suicide attempts are more common.
Other cultures and ethnicities.

Nonetheless, these findings provide important preliminary evidence that psychological risk factors for suicide change in potency across the lifespan.

They suggest the value of targeted early interventions and continued socioeconomic supports based on individuals’ levels of intelligence and emotional control.

References

Study: How intelligence and emotional control are related to suicidal behavior across the life course – a register-based study with 38-year follow-up
Authors: Nora Hansson Bittar et al. (2020)