The unexpected mental health consequences of veganism, according to medical research

Vegan diets are on the rise—but a growing body of research raises unexpected questions about their impact on mental health. A closer look at the data reveals patterns that many haven’t yet considered. While plant-based diets continue to surge in popularity, a comprehensive review published in Cureus reveals a troubling pattern that deserves attention. The research, which analyzed 18 studies involving over 160,000 participants, found that people following vegan diets face significantly higher risks of depression, anxiety, and other mental health challenges than their omnivorous counterparts. The numbers are stark. According to the Cureus review, vegans showed a 35.2% lifetime prevalence of depression compared to 19.1% in meat-eaters. For anxiety disorders, the gap was similarly pronounced: 31.5% lifetime prevalence in vegans versus 18.4% in meat-eaters. Perhaps most tellingly, 11 of the 18 studies examined found that meat-free diets were associated with worse psychological health. These findings align with a meta-analysis published in Nutrition Reviews, which found that vegans and vegetarians were at more than double the risk for depression compared to omnivores, with an odds ratio of 2.142. What's driving this mental health crisis? Researchers point to several critical nutrient deficiencies endemic in unsupplemented vegan diets, with vitamin B12 deficiency emerging as a primary concern. The Cureus review notes that this essential nutrient, found almost exclusively in animal products, plays a crucial role in neurological function and mood regulation. Low B12 levels have been directly linked to neurologic and hematologic problems. The implications extend beyond mood disorders. Research published in Molecular Nutrition & Food Research suggests that B12 deficiency may increase cancer risk. The study found that "a B12 deficiency leads to increased uracil misincorporation, leading to impaired DNA synthesis and genomic instability," and causes "global hypomethylation of DNA, a hallmark of early carcinogenesis." But B12 isn't the only concern. The Cureus review identifies multiple nutrients commonly deficient in vegan diets: zinc, which has poor bioavailability in plant foods and is linked to depression; iron, as non-heme iron from plants is less bioavailable than heme iron from meat; and vitamin D and calcium, with insufficient intake linked to increased fracture risk and potential mood disorders. Perhaps most concerning is the emergence of orthorexia nervosa—an obsessive fixation on "healthy" eating—among vegan populations. The Cureus review notes that "vegetarian, and vegan, women are more prone than males to have disordered eating attitudes and practices." This observation is supported by research published in Eating and Weight Disorders, which found that individuals following a vegan diet showed higher levels of orthorexic behaviors compared to omnivores. The researchers observed that "a vegan diet might become a guise for disordered eating, including for orthorexia nervosa, and might provide an excuse for following food rules that result in the removal of whole food groups." Certain populations appear particularly vulnerable. According to the Cureus review, women "notably appeared to be adversely impacted by mental disorders such as stress." The research also raises serious concerns about pregnant women, finding that "the vegan diet was substantially linked with an elevated risk of small-for-gestational-age infants" with significantly lower birthweights compared to babies born to omnivorous mothers. The relationship between veganism and mental health is complex. Research published in Nutrition Bulletin notes that while 44% of reviewed outcomes indicated vegetarian and vegan diets were associated with higher rates of depression, the relationship may involve reverse causation. As the researchers explain, "individuals who have psychosocial disorders may be more inclined to follow a vegetarian or vegan diet in order to improve their mental health." Despite these concerns, experts emphasize that awareness and proper supplementation are key. Researchers from the Quadram Institute warn of "a quiet epidemic of vitamin B12 deficiency in people who follow increasingly popular plant-based diets," with deficiency rates as high as 62% in pregnant vegan women. Professor Martin Warren from the Quadram Institute states: "There are many good reasons to follow a planned and balanced plant-based diet but for a vegan diet especially you should be aware of the potential for nutritional deficiency and the need to take appropriate vitamin B12 supplements." His colleague, Dr. Kourosh R Ahmad, adds: "Our paper is not about convincing people they are wrong for becoming vegans, but about making sure they are safe and don't sleepwalk into being B12 deficient." The message emerging from this body of research is nuanced but clear. While plant-based diets offer documented benefits for cardiovascular health and environmental sustainability, they require careful planning and supplementation to avoid potentially serious mental health consequences. As the Cureus review authors conclude: "Given the growing interest in diets without animal protein intake in the general population, it is crucial, now more than ever, to have a clear understanding of both the risks and benefits of such diets among clinicians, policymakers, and the public." For those committed to plant-based eating, the research suggests several essential steps: regular B12 supplementation or consumption of fortified foods, vitamin D supplementation especially in winter months, consideration of algae-based omega-3 supplements, regular blood work to monitor nutrient levels, and consultation with healthcare professionals familiar with plant-based nutrition—particularly for vulnerable populations including women, adolescents, and those with existing mental health conditions.