It is unclear whether having a low or high IQ in childhood precedes depression in adulthood. Researchers are continuing to investigate how IQ affects a person’s likelihood of developing depression.

Depression as a mood disorder cannot be explained by a singular cause, and a culmination of factors influences the type and severity of depression someone experiences.

Defining intelligence is also a complicated task, and it involves memory recall, rational thinking, and decision-making. All of this may be measurable on an intelligence quotient (IQ) test, but these scores do not fully account for emotional intelligence, learned experience, cultural differences, health status, access to schooling, and more.

Read on to learn more about the link between depression and intelligence.

A chess board with unmoved chess pieces.Share on Pinterest
Getty Images

Depression is the most common mental health disorder worldwide, involving symptoms that affect a person’s concentration, self-esteem, physical health, and overall quality of life.

Efforts to understand depression have led researchers to similar but diverging theories on the value of assessing intelligence as a precursor to various mental health conditions.

The theories respectively fall within three categories:

  • low to borderline IQ (<70–85) could increase psychiatric risk
  • high IQ (>130) could increase psychiatric risk
  • high IQ has no effect on depression or psychiatric risk but could be a protective factor

An older study from 2009 observed an association between low IQ in childhood and major depression in adulthood.

The findings are based on observations from a group of 1,037 participants whose IQ was tested three times from ages 7–11. After years of follow-up, researchers noted a link between lower IQ test results and depression diagnoses in adulthood.

Meanwhile, they found that higher IQ was associated with a reduced risk of post-traumatic stress disorder (PTSD), anxiety, and social phobia.

The researchers highlight many limitations to the study, however. This includes recall bias (meaning the participants could have misremembered a depressive episode), study size, and study duration. Because the study ended when the participants were 32, it is unclear what effect IQ has on psychiatric risk in older adults.

Conversely, a 2018 observational study suggested that people with high IQ could be more prone to hypersensitive and overexcitable brain or body responses. In other words, having a higher IQ could predispose a person to upregulated central nervous system functioning that favors inflammation, stress, and consequently, depression.

A 2022 study published in European Psychiatry has since refuted the theory that people with higher IQs have more mental health disorders, citing misrepresentative sampling methods in older research.

Pulling data from thousands of people logged in the UK Biobank, researchers found that people with higher intelligence did not have higher rates of depression. In fact, they had less anxiety, PTSD, neurotic tendencies, and trauma than those with lower intelligence.

The idea that low or high IQ predicts worse or more favorable health outcomes remains disputed in large part due to sampling bias and limitations in study sizes.

People with higher intelligence, having taken an IQ test or not, may show signs of:

These traits do not factor in personality or socioeconomic variables, though. This means that a person with a high IQ could behave or think differently than someone with the same IQ.

In addition to depression, researchers also see correlations between varying levels of intelligence and other psychiatric illnesses, including:

Additionally, there is speculation that intelligence decreases and even affords protection against neuroticism, a personality trait involving high emotional and stress sensitivity, but not major depression.

Learn about how neuroticism differs from depression.

Everyone experiences depression differently. Feelings of despair, disinterest in hobbies or activities, appetite changes, fatigue, and self-doubt are a few of the symptoms of depression.

A doctor or mental health professional can help people discern their feelings and guide them to the appropriate treatment.

Many therapists offer sliding scale payment options, host virtual sessions, and can be found through online databases.

Depression and intelligence do not have a linear or causal relationship. Someone with a low, average, or high IQ can develop depression.

It is thought that measures of intelligence may influence a future psychiatric diagnosis.

Because there are many risk factors for depression, including trauma, chronic illness, and genes, a person should consult a doctor if they are experiencing symptoms.