A major new study led by researchers at St. Michael’s Hospital in Toronto has taken a close look at how ketogenic diets may affect depression and anxiety in adults.
The findings suggest that keto diets may offer some help for people with depressive symptoms, although the evidence for anxiety remains unclear.
The study brings together 50 years of research and includes data from almost 42,000 adults from 15 different countries, making it one of the largest reviews ever done on this topic.
A ketogenic diet is a way of eating that is very low in carbohydrates, high in fats, and moderate in protein. It was first used 100 years ago to treat epilepsy in children who did not respond to medication.
The diet forces the body to switch its main fuel source from sugar to ketone bodies, which are produced when the body burns fat. This shift changes how the brain works and may reduce inflammation, improve energy use, and help brain cells function more efficiently.
Scientists have long suspected that problems in cell energy, inflammation, and glucose processing may play a role in depression, bipolar disorder, and schizophrenia.
Because the ketogenic diet affects all of these areas, researchers have wondered whether it might also help people with mental health conditions. Some early case reports have suggested that people following a keto diet felt improvements in mood, thinking, and overall quality of life.
To understand the bigger picture, the new study reviewed 50 studies published between 1965 and 2025. These included randomized clinical trials, case reports, case series, cross-sectional research, and quasi-experimental designs.
Together, these studies included more than 41,000 adults ages 18 to 70. Some participants had mental health conditions such as major depressive disorder, generalized anxiety disorder, bipolar disorder, schizophrenia, or PTSD. Others were from non-psychiatric groups, such as people with obesity or metabolic problems.
The researchers looked only at studies that used proper psychiatric measurement tools, such as the PHQ‑9 for depression and the GAD‑7 for anxiety. This helped ensure that the results were based on reliable and repeatable measures.
The strongest findings were related to depression. Ten randomized clinical trials with 631 participants showed that people on ketogenic diets had a small to medium improvement in depressive symptoms compared to people on other diets.
The improvement was much stronger in studies that used biochemical monitoring to confirm that people really entered ketosis. In those studies, the improvement was closer to a medium-to-large effect. This suggests that staying in true ketosis may be important if someone wants to see mental health benefits.
The type of comparison diet also mattered. When keto diets were compared with low-carbohydrate or balanced diets, results were mixed. But when they were compared with high-carbohydrate diets, the keto group did not show a clear advantage.
Interestingly, people without obesity benefited more from ketogenic diets than people with obesity. This may reflect differences in metabolism, inflammation, or diet adherence.
The severity of carbohydrate restriction also made a difference. People following very strict ketogenic diets (10% or less of calories from carbs) showed a noticeable improvement in mood. People following less strict low-carb diets (11% to 20% carbs) did not show strong changes.
A second group of studies—called quasi-experimental studies—also supported the idea that keto diets may help reduce depressive symptoms. These studies were not as tightly controlled as clinical trials, but they still showed meaningful improvements in mood over time.
The picture for anxiety was much less clear. In high-quality randomized clinical trials, ketogenic diets did not show a meaningful improvement in anxiety symptoms. But in quasi-experimental studies, people did report feeling less anxious over time while following keto diets.
It is hard to know whether the changes came from the diet itself or from other factors like weight loss, lifestyle changes, or stronger motivation among participants who stuck to the diet.
Some smaller case reports and case series described impressive improvements in people with bipolar disorder or schizophrenia, including fewer psychotic symptoms and better mood stability. However, these reports involved very small numbers of people and cannot be taken as proof.
Overall, the study authors caution that ketogenic diets are not a cure for depression or anxiety, and the results do not prove that the diet directly causes improvements.
The studies reviewed used many different types of keto diets, lengths of treatment, and levels of support. Many were short term, and long-term results are still unknown. Some people may benefit, while others may not notice any change at all.
The findings show that ketogenic diets may help reduce depressive symptoms in some adults, especially when the diet is followed strictly enough to achieve ketosis. For anxiety, the evidence is not yet strong enough to draw conclusions.
More research is needed to understand who might benefit the most and how to use the diet safely, especially for people taking multiple medications or people with medical conditions.
If you care about health, please read studies that scientists find a core feature of depression and this metal in the brain strongly linked to depression.
For more health information, please see recent studies about drug for mental health that may harm the brain, and results showing this therapy more effective than ketamine in treating severe depression.
The study is published in JAMA Psychiatry.
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