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August 15, 2024
A placebo is a pill that does not contain any active medication. It is given to patients who form the control group in clinical trials. Comparing the effects of a treatment with placebo is essential because some patients will improve with the passage of time and some will get better due to the expectation of benefit they have from being enrolled in a clinical trial.
In studies of psychiatric conditions, patients in placebo groups typically show improvement. This can be induced by combinations of hope, suggestion, expectation, and consumption of what are presented as medications. It is reinforced by the context of receiving compassionate care from others, with supportive conversations.
A 2005 study found that placebo response is unequally distributed across psychiatric disorders, but did not address several disorders (including bipolar disorder) examined in the present meta-analysis conducted by a German research team.
Using only high-quality randomized clinical trials (RCTs) across major psychiatric diagnoses, the team quantified differences in the change of disorder symptoms within placebo groups.
They selected nine common and clinically significant psychiatric conditions: major depressive disorder (MDD), mania (bipolar disorder), schizophrenia, obsessive-compulsive disorder (OCD), attention-deficit/hyperactivity disorder (ADHD), generalized anxiety disorder (GAD), panic disorder, posttraumatic stress disorder (PTSD), and social phobia. For each of these, they selected the ten most recent high-quality RCTs of medicationsfor meta-analysis.
Of the ninety included RCTs, the team only looked at placebo groups. Because RCTs for the different diagnoses used differing established psychopathology rating scales, standardized pre-post effect sizes were used to compare outcomes across diagnoses.
Meta-analysis of the ten ADHD RCTs with a combined total of 1,189 participants reported large effect size improvements in symptoms, with no variation (heterogeneity) across RCTs and no sign of publication bias.
By contrast, the placebo effect size improvements in symptoms of major depressive disorder (10 RCTs, 1,598 participants) and generalized anxiety disorder (10 RCTs, 1,457 participants) were very large, well above those for ADHD, and with no overlap of 95% confidence intervals.
At the other end of the spectrum, the placebo effect size improvements in symptoms of schizophrenia (10 RCTs, 888 participants) were moderate, well below those for ADHD, and with no overlap of 95% confidence intervals.
There were absolutely no indications of publication bias.
The team noted, “In all diagnoses, there were improvements in symptom severity during placebo treatment (ie, the lower limit of the 95% CIs of the pooled pre-post placebo effect sizes were >0).” Although they stated, “The large and robust improvements observed in ADHD studies have not been reported to our knowledge.” they seemed to have missed this article by me and my colleagues: https://pubmed.ncbi.nlm.nih.gov/34232582/.
They also concluded, “Comparing the courses of different disorders under placebo indirectly may assist in understanding disease etiology, possibly providing insights into the proportionate influence of organic and psychogenic factors. Conditions with presumed substantial hereditary and biological components, such as schizophrenia, exhibited modest placebo responses in our analysis. Conversely, disorders with potentially less biological contribution, eg, depression and GAD, showed stronger responses. Our study may serve as an initial framework for incorporating the comprehensive insights derived from placebo groups of controlled trials into the etiopathogenetic exploration of mental illnesses.”
Yanli Zhang-James, John W.S. Clay, Rachel B. Aber, Hilary M. Gamble, Stephen V. Faraone,
Post–COVID-19 Mental Health Distress in 13 Million Youth: A Retrospective Cohort Study of Electronic Health Records,
Journal of the American Academy of Child & Adolescen
Tom Bschor, Lea Nagel, Josephine Unger, Guido Schwarzer, and Christopher Baethge, “Differential Outcomes of Placebo Treatment Across 9 Psychiatric Disorders: A Systematic Review and Meta-Analysis,” JAMA Psychiatry (2024), https://doi.org/10.1001/jamapsychiatry.2024.0994.
Faraone, S. V., Newcorn, J. H., Cipriani, A., Brandeis, D., Kaiser, A., Hohmann, S., Haege, A. & Cortese, S. (2021). Placebo and nocebo responses in randomised, controlled trials of medications for ADHD: a systematic review and meta-analysis. Mol Psychiatry 27, 212-219.
The Background:
Previous research has suggested that people with ADHD have higher rates of death than those without the condition. Until now, many of those studies lacked the detail needed to untangle why this might be the case. A recent meta-analysis of eight separate studies reported that ADHD roughly doubled the risk of death, and it hinted that factors like socioeconomic status and other mental illnesses might help explain the link.
The Study:
To explore this in more detail, researchers used the US National Health Interview Survey, a nationally representative prospective cohort of just over 52,000 adults. Survey records were linked with the National Death Index, and participants were followed from the date of interview until death or December 31, 2019, whichever came first. The main outcome was death from any cause. With a median follow-up of just under eight years, there were 6,024 deaths recorded.
When the team adjusted their analysis for age, sex, ethnicity, and the year of the survey, having ADHD was associated with a 58% higher risk of death. Controlling further for family income and educational level reduced that increased risk slightly, to 50%.
Controlling for health conditions (like high blood pressure, diabetes, stroke, heart disease, and cancer) and lifestyle factors (smoking, alcohol use, physical activity, and body weight) also reduced the association to about 46%.
By contrast, when the researchers adjusted for two psychiatric conditions (anxiety and depression) commonly found alongside ADHD, the link between ADHD and higher mortality disappeared statistically. In other words, once anxiety and depression were taken into account, ADHD itself was no longer associated with a clearly measurable increase in the risk of death.
What Does This Mean?
The authors conclude that the apparent effect of ADHD on mortality seems to operate largely through accompanying mental illness, and to a lesser extent through lifestyle and physical health problems. They suggest that treating and managing these co-occurring issues (through medications, therapy, and behavioral interventions) might help reduce the risk of premature death in people with ADHD, although they note that further evidence is needed.
The Background:
Dementia is a rapidly growing public health problem affecting more than 50 million people worldwide. Nearly 10 million new cases are diagnosed each year, and that number is expected to almost triple by 2050. The most common form is Alzheimer’s disease, accounting for roughly 60–70% of cases, followed by vascular dementia at around 20%. Other types include dementia with Lewy bodies, Parkinson’s disease dementia, and frontotemporal dementia. While no cure exists, managing modifiable risk factors (such as high blood pressure, smoking, physical inactivity, and poorly controlled diabetes) can delay or slow both the onset and progression of the condition.
Several studies have reported an elevated dementia risk among people with ADHD, and a number of mechanisms may explain this association. These include shared genetic or neurobiological vulnerabilities, reduced cognitive reserve (leaving the brain less resilient to age-related damage), and greater lifetime exposure to other established dementia risk factors.
Earlier reviews explored the possible link between ADHD and dementia, but tended toward a broader scope (incorporating other neurodegenerative disorders or mixing study designs), which introduced substantial variability and precluded quantitative synthesis. The relevant research literature has also expanded considerably since those reviews appeared.
The Study:
This meta-analysis restricted inclusion to case-control and cohort studies, yielding five that met the criteria. One was a case-control study with 400 participants; the other four were cohort studies collectively covering 3.7 million individuals, two retrospective and two prospective.
The Results:
Pooling the four cohort studies, individuals with ADHD showed approximately two-and-a-half times the dementia risk of those without the diagnosis. There was no indication of publication bias.
The Take-Away:
The authors concluded that ADHD is associated with a significantly increased risk of all-cause dementia in later life, while noting that its relationship to specific dementia subtypes remains less clear and warrants attention in future research.
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The Background:
Women with polycystic ovary syndrome (PCOS) themselves show higher rates of ADHD. Because ADHD is partly heritable (meaning genes contribute to the condition), some of the increased ADHD seen in children of mothers with PCOS could come from shared genetic factors. In other words, a mother’s and her child’s increased risk might sometimes reflect common genes rather than an effect of the pregnancy itself.
Beyond genetics, growing evidence points to maternal metabolic problems during pregnancy as another important risk factor for neurodevelopmental outcomes. PCOS is one of these conditions and is considered both potentially modifiable (treatable or manageable) and biologically plausible as a contributor to risk. PCOS affects an estimated 5–10% of women of reproductive age worldwide and is characterized by signs such as hyperandrogenism (higher-than-normal levels of “male” hormones), insulin resistance (poorer ability to use the hormone insulin, which can affect blood sugar and metabolism), and chronic low-grade inflammation.
However, studies to date have not all reached the same conclusions. Some research suggests the association between maternal PCOS and offspring ADHD is stronger for girls, while other studies did not analyze results by child sex. Methodological differences make it harder to draw clear conclusions.
The Study:
It’s important to note that the studies included in this meta-analysis were observational (cohort studies and case-control studies). Observational studies can identify associations (that two things occur together) but cannot prove that one causes the other. A cohort study follows people over time, and a case-control study compares people with a condition to similar people without it.
The pooled results came from six studies that together included almost 1.4 million mother–child pairs and that adjusted for confounders (other factors that might influence the result, such as maternal age or socioeconomic status). After statistical adjustment, children of mothers with PCOS had about 40% greater odds of ADHD than children of mothers without PCOS. The analysis reported no evidence of publication bias (no clear sign that only positive studies were published) and zero heterogeneity (the results were consistent across the studies).
There was no meaningful difference in results between cohort and case-control studies, and the meta-analysis did not find a significant difference in the association when comparing male and female offspring.
The Take-Away:
The research team concluded that this large-scale synthesis found an association between maternal PCOS and higher odds of ADHD and other neuropsychiatric conditions in children. They suggested that children born to mothers with PCOS may benefit from developmental monitoring to identify and address problems early, while emphasizing that causal relationships have not been established. They called for further studies to confirm these findings and to investigate the biological and environmental mechanisms that might explain the association. Indeed, because women with PCOS show higher rates of ADHD than other women, we need genetically informed research designs to see if the reported association is confounded.
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