A low-carbohydrate ketogenic diet may help ease symptoms in adults with treatment-resistant depression, according to new research from the United Kingdom. However, the benefits appear to diminish over time, raising questions about its long-term effectiveness.

The study, published in JAMA Psychiatry, explored whether dietary changes could offer relief to people whose depression has not improved after trying at least two different antidepressant medications — a condition known as treatment-resistant depression.

Depression remains one of the most common mental health conditions in the United States and globally. While many patients respond to medication or therapy, a significant number continue to struggle with persistent symptoms. Growing evidence suggests that nutrition may play a role in mental health, prompting researchers to examine whether a ketogenic, or “keto,” diet could make a difference.

The trial included 88 adults between the ages of 18 and 65. Participants were randomly assigned to follow either a ketogenic diet or a comparison “phyto” diet for six weeks.

The keto diet limited carbohydrate intake to 30 grams or less per day and emphasized higher fat consumption to induce ketosis — a metabolic state in which the body burns fat for fuel instead of carbohydrates. Prepared meals were provided to help participants adhere to the plan.

The control group followed a diet rich in fruits and vegetables, adding at least one extra serving daily and replacing saturated fats with unsaturated fats. Both groups received coaching and were instructed to maintain their weight, ensuring that any mood improvements could not be attributed to weight loss.

Researchers assessed depression symptoms using the Patient Health Questionnaire (PHQ-9), a widely used screening tool. They also monitored anxiety and other mental health measures.

After six weeks, both groups showed improvement in depressive symptoms. However, the keto group experienced a slightly greater reduction. On average, depression scores dropped by about 10 points in the keto group compared to an 8-point reduction in the phyto group. Additionally, 25% of participants in the keto group achieved remission at six weeks, compared with 9% in the comparison group.

But the encouraging results appeared to fade over time.

At the 12-week follow-up, adherence to the keto diet had declined significantly. About half of the keto participants had stopped following the diet altogether, and only a small fraction continued it nearly every day. Depression scores in both groups declined slightly further, but the gap between the two diets narrowed, suggesting the keto diet’s advantage may be short-lived.

Researchers also noted that participants with more severe depression at the start of the study appeared to benefit more from the ketogenic diet than those with moderately severe symptoms.

Despite the promising early findings, the overall difference between the two groups did not reach the researchers’ threshold for clear clinical significance. They had hoped to see a five-point greater improvement in the keto group compared to the phyto group, a benchmark that was not met.

The researchers concluded that while the ketogenic diet may offer short-term symptom relief for some individuals with treatment-resistant depression, its long-term benefits remain uncertain. They emphasized the need for larger and longer studies to better understand whether dietary interventions can play a sustained role in managing difficult-to-treat depression.

The findings add to a growing body of research exploring how metabolic health and nutrition may influence brain function and mood — an area that continues to attract increasing scientific interest.