Poverty Causally Linked to Mental Illness and Vice Versa

There is a bidirectional, causal relationship between mental illness and poverty, new research showed.

“This study indicates that certain mental health problems can make a person’s financial situation uncertain. But conversely, we also see that poverty can lead to mental health problems,” study investigator Marco Boks, MD, PhD, corresponding author, Amsterdam University Medical Center, Amsterdam, the Netherlands, said in a press release.

The findings were published online on July 10, 2024, in Nature Human Behavior.

Disentangling Cause and Effect

Previous research shows a correlation between poverty and mental illness, but the direction of the association has always been uncertain and complicated by factors such as stress, housing insecurity, and substance use.

To investigate a potential causal relationship between poverty and mental illness, investigators used data from more than 500,000 participants in the UK Biobank and the international Psychiatric Genomic Consortium, including 18 genome wide association studies.

Investigators developed a measure of poverty based on household income, occupational income, and social deprivation. They then examined the causal relationship of poverty on nine mental illnesses. These included attention-deficit hyperactivity disorder (ADHD), anorexia nervosa (AN), anxiety disorder, autism spectrum disorder, bipolar disorder, major depressive disorder (MDD), obsessive-compulsive disorder, posttraumatic stress disorder, and schizophrenia.

They also extended the analyses to potential confounders such as cognitive ability.

Using genomic structural equation modeling, the team found a causal bidirectional relationship between poverty, ADHD, and schizophrenia. They found that lower income was causally related to these disorders and that there was also a causal relationship between the disorders and lower income.

They also found a one-directional causal effect of poverty on MDD and an inverse causal relationship between poverty and AN, which was causally associated with higher incomes (all P < .05).

“This evidence supports a vicious cycle between poverty and severe mental illness,” the authors noted.

The effects of poverty on mental illness were reduced by approximately 30% when investigators adjusted for cognitive ability.

The investigators noted that the generalizeablity of the findings are limited because most of the genetic studies were conducted in populations of European ancestry from high-income countries. In addition, they noted that psychiatric phenotypes are complex and heterogeneous, which generally translates to low power.

“The findings of this study reiterate the need to further unravel the roles of poverty and mental illness and to use this insight to advance mental health for all. The choice of which action to take to address the problem is a political matter, but attention is warranted considering increasing income inequalities worldwide, as well as the increasing incidence of mental illness,” the researchers noted.

There was no funding information available for the study, and there were no disclosures from authors.