Chemical Imbalance Myth Influences Patients’ Beliefs About Antidepressants

By Carrie Clark

The results of a new survey published in the Journal of Affective Disorders highlight the ongoing influence of the "chemical imbalance" theory and the myth of the "chemical cure." Researchers Mollie Griffin Williams, Mark Horowitz, James Davies, and Joanna Moncrieff show that belief in debunked biological theories about the causes of mental health conditions has declined since the 2010s. Even so, the survey finds that such theories continue to negatively shape outcomes for a significant proportion of patients.

Four hundred ninety-seven people enrolled in a free talk therapy service in the UK, all of whom had taken or were taking antidepressants, were asked two questions about what they thought had caused their original mental health condition and how they believed antidepressants worked.

Across both questions, 57% of respondents believed either that their mental health condition was caused by a biological deficit or that antidepressants worked by fixing such a deficit. As the researchers point out, this is a lower rate than that found in previous studies, where 80% or more of people were found to hold biological beliefs about the causes and treatment of mental health conditions.

“While belief in the ‘chemical imbalance’ theory of mental health conditions is declining, the myth of the ‘chemical cure’ is alive and well.”

However, examining the answers to the two questions separately reveals an interesting divergence. While 40.8% of respondents endorsed a belief that mental health conditions were biological in origin, a higher rate of 52.3% believed that antidepressants work by correcting a biological deficit. It seems that some patients rejected a biological explanation of their mental health problem while nonetheless continuing to believe that antidepressants are targeted biological treatments. This suggests that while belief in the "chemical imbalance" theory of mental health conditions is declining, the myth of the "chemical cure" is alive and well.

This really matters because the survey results show that patient beliefs shape the course of antidepressant treatment in powerful and far reaching ways. Perhaps unsurprisingly, respondents who held biological beliefs were more likely to report that they did not believe they could cope without antidepressants. While they were more likely than those who did not hold biological beliefs to report a positive experience of taking antidepressants, they were also more likely to take the drugs for extended periods of time and were less likely to have ever tried to stop.

“There is mounting evidence that antidepressants have very limited efficacy and, as the researchers point out, every reason to believe that many long-term users are taking the drugs unnecessarily.”

Importantly, this longer duration of use was not associated with greater severity of original anxiety or depression symptoms, meaning that it’s not just the case that participants with biological beliefs had more serious mental health problems to start with and therefore "needed" to take the drugs for longer. In fact, there is mounting evidence that antidepressants have very limited efficacy and, as the researchers point out, every reason to believe that many long-term users are taking the drugs unnecessarily.

In this context, in which we might hope to see efforts to reduce unnecessary antidepressant prescribing, duration of use becomes critically important. Research on antidepressant withdrawal consistently finds that longer duration of use is associated with greater number and severity of withdrawal symptoms on cessation, a finding replicated in this survey. Intriguingly, while perceptions of treatment efficacy were heavily mediated by patient beliefs, withdrawal effects were not. Among the 310 respondents who had ever tried to stop taking an antidepressant, holding biological beliefs had no impact on the number or severity of withdrawal symptoms experienced, or on the success or failure of the attempt to stop.

“Antidepressant treatment effects are highly subjective, with the beliefs of the patient powerfully influencing whether or not the drugs are perceived to be effective.”

It’s worth dwelling for a moment on the significance of this finding. This survey joins others in showing that antidepressant treatment effects are highly subjective, with the beliefs of the patient powerfully influencing whether or not the drugs are perceived to be effective. Moncrieff has demonstrated that the limited efficacy shown by antidepressants in drug trials is likely to be accounted for by amplified placebo effects, and it’s reasonable to infer that the more positive reports of antidepressant effects found by this survey among people who hold biological beliefs are attributable to these effects. Put simply, if you believe that your distress is due to a biological deficit that is corrected by antidepressants, then you are primed to believe that the drugs are effective, regardless of their objective effects.

However, the survey results suggest that withdrawal effects are not likewise mediated by the subjective beliefs of patients. Instead, respondents reported experiencing withdrawal effects on cessation regardless of what they believed about the causes of mental health conditions or the mechanism of antidepressant action. Given the tendency of withdrawal-skeptical psychiatrists to attribute withdrawal symptoms to the nocebo effect, or to claim that people harmed by psychiatric drugs are simply imagining their symptoms, this is quite ironic. This survey suggests quite the opposite: the suffering caused by withdrawal is an objective reality in a way that the supposed benefits of antidepressant treatment effects are not.

Photo by Ksenia Yakovleva on Unsplash