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August 4, 2020 by Ana Florence, PhD |

Disproven Chemical Imbalance Theory Leads To Worse Depression Outcomes

A new study finds that biological explanations for depression, including the disproven “chemical imbalance” theory, lead to poor expectations of improvement and more depressive symptoms after treatment.

A new study, published in the Journal of Affective Disorders, found patients who believe that a chemical imbalance in the brain causes depression to have worse treatment outcomes. The study was led by Hans S. Schroder, a post-doctoral researcher and clinician at the Harvard Department of Psychiatry.

The results of the study, which included a sample of 279 persons attending an intensive behavioral health program in the United States, found that the endorsement of the chemical imbalance theory of depression was associated with poorer expectations of treatment and lower perceived credibility. Additionally, the researchers found that a belief in biological causes for depression was predictive of a greater presence of depressive symptoms at the end of treatment. Schroder and his colleagues write:

“Our findings are in line with accumulating evidence that some biogenetic beliefs, like the chemical imbalance belief, are linked with poorer expectations for improvement, especially among those with the most troubling symptoms.”

Many different explanations for the causes of emotional distress have been proposed. In recent years, the psychosocial model, which emphasizes the relationship between the environment and individual characteristics, has been widely accepted. However, biological explanations remain popular and are endorsed among mental health professionals and service users alike.

Despite growing evidence that biological explanations for emotional distress do not reduce stigma and lack scientific credibility—there is no evidence that chemical imbalances cause mental illnesses in the brain—this belief remains widespread. The defunct chemical imbalance theory, which was widely promoted by drug companies, remains prevalent on mental health websites and has been connected to both increased antidepressant prescribing and increased difficulty withdrawing from antidepressants.

Schroder and colleagues argue that beliefs in biological explanations can have adverse effects on treatment outcomes. Research suggests that persons who explain their emotional distress through chemical imbalances in the brain may feel less hopeful that they might get better and less in control of their recovery process.

According to the authors, the chemical imbalance explanation leads to an essentialist understanding of emotional distress, meaning that individuals believe that their difficulties arise from traits that cannot be changed: “biogenetic beliefs and explanations may inadvertently promote prognostic pessimism,” they explain. Additionally, the chemical imbalance explanation leads to lower treatment expectations for psychotherapy and higher expectation that medications may be beneficial.

This is the first study to assess whether there is a relationship between the biological beliefs of the causes of emotional distress and treatment outcomes in a real-world clinical setting. The authors hypothesized that in the sample of 279 persons, “biogenetic beliefs would be at least as strongly endorsed as psychogenic beliefs […] beliefs would be negatively related to treatment expectations and perceived credibility of the treatment program […] greater biogenetic beliefs would predict poorer treatment outcomes.”

Through a series of measures and scales about individual’s beliefs regarding the causes of depression and treatment expectations, diagnostic tools, and self-reported psychiatric history, the authors were able to run a series of statistical tests to determine the relationship between etiological beliefs and treatment outcomes.

The treatment program consisted of a wide array of offerings, including medication, group therapy, and case management. Individuals were hospitalized for an average of 12.6 days, and most were diagnosed with a major depressive episode.

The authors found less favorable treatment-relevant processes were associated with the endorsement of biologic beliefs:

“For individuals with more depressive symptoms, both chemical imbalance and genetic beliefs were associated with poorer treatment expectations and perceived credibility. We also found evidence that the chemical imbalance belief, but not the genetic belief or the psychogenic beliefs, predicted more depressive symptoms after the brief treatment program using a two-week, but not 24-hour, measure of depression.”

The adoption of such beliefs can be explained by a widespread narrative of the chemical imbalance hypothesis present not only in the discourse of mental health professionals but in the media, television advertisements, and public health campaigns. Additionally, nearly all participants in this study were prescribed at least one psychiatric drug, perhaps reinforcing the biologic etiology belief:

“Merely taking medication may reinforce the putative biochemical origins of the problem. If so, extensive psychiatric care may reinforce biogenetic beliefs in highly depressed patients —those most sensitive to the negative consequences of the beliefs.”

This study provides relevant evidence that the chemical imbalance theory of psychological distress may have negative impacts on psychotherapeutic processes and act as a barrier to improvement. This study must be read side by side with the growing body of evidence showing that psychiatric drugs can have long-term disabling effects, cause severe withdrawal symptoms, and provide little if any improvement compared to placebo.

It is both timely and urgent that providers, clinicians, and policymakers review how to discuss treatment options, what messages should be offered to the public and what treatment modalities effectively improve hope that recovery is possible.



Schroder, H. S., Duda, J. M., Christensen, K., Beard, C., & Björgvinsson, T. (2020). Stressors and chemical imbalances: Beliefs about the causes of depression in an acute psychiatric treatment sample. Journal of Affective Disorders. 537-545. (Link)

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