A study of 1.2 million people in the United States conducted by Yale researchers has found that people who exercise report having 1.5 fewer days of poor mental health a month, compared to people who do not exercise.The study, published in The Lancet Psychiatry journal, found that team sports, cycling, aerobics and going to the gym are associated with the biggest reductions, according to a press release issued August 8 by the journal.More exercise was not always better, and the study found that exercising for 45 minutes three to five times a week was associated with the biggest benefits.The analysis, the largest observational study of its kind, included all types of physical activity, ranging from childcare, housework, lawn-mowing, and fishing to cycling, going to the gym, running, and skiing.Exercise reduces the risk of cardiovascular disease, stroke, diabetes, and mortality from all causes, but its association with mental health remains unclear.Previous research into the effect of exercise on mental health has conflicting results. While some evidence suggests that exercise may improve mental health, the relationship could go both ways – for example inactivity could be a symptom of and contributor to poor mental health, and being active could be a sign of or contribute to resilience. The authors note that their study cannot confirm cause and effect.“Depression is the leading cause of disability worldwide, and there is an urgent need to find ways to improve mental health through population health campaigns,” said Adam Chekroud, PhD, Assistant Professor of Psychiatry, Chief Scientist at Spring Health, USA, and the study's senior author. “Exercise is associated with a lower mental health burden across people no matter their age, race, gender, household income and education level. Excitingly, the specifics of the regime, like the type, duration, and frequency, played an important role in this association. We are now using this to try and personalize exercise recommendations, and match people with a specific exercise regime that helps improve their mental health.”Depression is the leading cause of disability worldwide, and there is an urgent need to find ways to improve mental health through population health campaigns.Adam Chekroud, PhD, Assistant Professor of PsychiatryOther Yale Department of Psychiatry affiliates who participated in the study were John H. Krystal, MD, Robert L. McNeil, Jr. Professor of Neuroscience and Chair of Psychiatry, and Ralitza Gueorguieva, PhD, Senior Research Scientist in Biostatistics and Director of Biostatistics in Psychiatry.\n In the study, the authors used data from 1.2 million adults across all 50 US states who completed the Behavioral Risk Factor Surveillance System survey in 2011, 2013, and 2015. This included demographic data, as well as information about their physical health, mental health, and health behaviors. The study did not take mental health disorders into account, other than depression.Participants were asked to estimate how many days in the past 30 days they would rate their mental health as "not good" based on stress, depression, and emotional problems. They were also asked how often they took part in exercise in the past 30 days outside of their regular job, as well as how many times a week or month they did this exercise and for how long.All results were adjusted for age, race, gender, marital status, income, education level, employment status, BMI, self-reported physical health, and previous diagnosis of depression.On average, participants experienced 3.4 days of poor mental health each month, according to the study.