Science news: Placebo effect for all psychiatric diagnoses “of considerable magnitude”


In a new study, researchers found huge improvements in psychiatric symptoms on placebo alone, particularly for depression and anxiety. They included the 10 least biased, most recent randomised controlled trials for nine common diagnoses in their attempt to quantify the improvements that could be expected without treatment.

“First, symptom improvement occurred in all conditions under placebo treatment. Second, the improvements were of considerable magnitude. Third, improvement varied significantly among disorders and was particularly strong in MDD and GAD,” the researchers write.

The study was led by Tom Bschor at the Technical University of Dresden, Germany. It was published in the top-tier journal JAMA Psychiatry.

Bschor and the other researchers identified nine major psychiatric diagnoses to investigate: major depressive disorder (MDD), mania, schizophrenia, obsessive-compulsive disorder (OCD), attention-deficit hyperactivity disorder (ADHD), generalised anxiety disorder (GAD), panic disorder, post-traumatic stress disorder (PTSD), and social phobia. They used the Cochrane Risk of Bias measure to select the 10 least biased randomised controlled trials for each diagnosis, using the most recent ones if there was a tie. They then pulled the standardised effect sizes for symptom improvement in the placebo group for each and averaged them for each diagnosis.

They controlled for a number of possible confounding factors, such as age, gender or sex, study duration and size, placebo randomisation probability, risk of bias, and year of publication.

Their main finding was that improvement was substantial in the placebo group for all nine diagnoses, with the largest effect sizes found in the MDD and GAD groups and the smallest found in the schizophrenia and OCD groups.

According to guidelines on interpreting effect size, the placebo responses for MDD, GAD, panic disorder, ADHD, and PTSD could all be considered large effects (above 0.8), and the remainder were at least moderate effects (above 0.5). The effect size for the placebo treatment of MDD was a massive 1.40, and the effect size for the placebo treatment of GAD was not far behind at 1.23.

“Even without systematic treatment,” the researchers write, “…meaningful improvements were evident.”

They also found that, across diagnoses, women were more likely to improve in the placebo group than men. This was true even after accounting for gender differences in diagnosis (since more women were found in the depression and anxiety groups). They were unable to explain this finding.

There was high heterogeneity between studies in terms of the placebo effect, so although the average effect was quite large, individual studies varied in terms of how large the effect actually was.

The researchers write that “this suggests prudence in drawing conclusions but is also unsurprising, considering internal and external influences, like study design and illness characteristics.” Indeed, they add that active treatment effects also vary quite a bit between studies.

Does Medication Lead to Better Outcomes or Worse?

Improvements in the placebo group include improvement that is actually due to “placebo” factors like expectation, attention, and hope, as well as statistical factors like regression to the mean. However, there are also improvements that are part of the normal course of the “illness.” Many psychiatric symptoms improve on their own. For instance, an NIMH study in 2006 found that 85% of untreated depressed patients recovered spontaneously within one year.

Worse, in many cases, psychiatric medication actually worsens outcomes. Compare that 85% recovery rate with no treatment to a recent study where over a thousand people with depression were treated with an intense program, beginning with antidepressant drugs (more than half on multiple drugs) and also including psychotherapy and hospitalisation, in which less than 25% even experienced “treatment response”, much less recovery.

For schizophrenia, too, studies have shown that those who reduce their dose or discontinue antipsychotic drugs have better outcomes in the long-term, including a higher likelihood of recovery as well as better social functioning, and a greater likelihood of employment.

Psychiatric drugs have common harms—including sexual dysfunction, weight gain, and emotional numbing with antidepressants, and metabolic dysfunctionheart problemsbrain damage, and Parkinson’s-like movement disorders with antipsychotics.

In the face of the dangers and poor outcomes for psychiatric drugs, a powerful placebo effect justifies beginning with watchful waiting—just giving a person time to improve on their own—before moving to exercise, and then perhaps to treatments that are less biologically harmful than psychiatric drugs, such as psychotherapy.

In fact, the latest guidance from the UK’s NICE suggests just this approach for less-severe depression, and the World Health Organization states that “antidepressant medications are not needed for mild depression.”

As Bschor and the other researchers involved in the current study write, “The more pronounced the improvement in the placebo groups, the more the treatment could at least initially be justified by the omission of medication.”



Bschor, T., Nagel, L., Unger, J., Schwarzer, G., & Baethge, C. (2024). Differential outcomes of placebo treatment across 9 psychiatric disorders: A systematic review and meta-analysis. JAMA Psychiatry. Published online May 29, 2024. doi:10.1001/jamapsychiatry.2024.0994 (Link)

This article was first published here on Mad in America.