Eating a Mediterranean-style diet — packed with fruits, vegetables, legumes, nuts, olive oil and fish — is good for your heart, many studies have found. Now scientists are suggesting the diet may be good for your mental health, too.

A study of over 10,000 Spaniards followed for almost four and half years on average found that those who reported eating a healthy Mediterranean diet at the beginning of the study were about half as likely to develop depression than those who said they did not stick to the diet.

All of the participants were free of depression when they were recruited to the study, and each filled out a 136-item food frequency questionnaire when they joined.

Based on their self-reported dietary habits, they were assigned a score between 0 and 9, with the highest score reflecting the closest adherence to a Mediterranean diet.

Over time, those who had scored between 5 and 9 on the Mediterranean diet were 42 percent to 51 percent less likely to develop depression, the study found, than those who scored between 0 and 2.

The study, which was funded by the Spanish government’s official medical research agency, Instituto de Salud Carlos III, does not prove a cause-and-effect relationship between the Mediterranean diet and a lower risk for depression, only an association between the two.

Still, many scientists are convinced that some damaging inflammatory and metabolic processes involved in cardiovascular disease may also play a role in mental health.

"Both cardiovascular disease and depression share common mechanisms related to endothelium function and inflammation,” said Dr. Miguel Angel Martinez-Gonzalez, professor of preventive medicine at University of Navarra in Pamplona, Spain, and senior author of the paper, published in the October issue of Archives of General Psychiatry.

"The membranes of our neurons are composed of fat, so the quality of fat that you are eating definitely has an influence on the quality of the neuron membranes, and the body’s synthesis of neurotransmitters is dependent on the vitamins you’re eating,” Dr. Martinez-Gonzalez added.

"We think those with lowest adherence to the Mediterranean dietary plan have a deficiency of essential nutrients.”

The elements of the diet most closely linked to a lower risk of depression were fruits and nuts, legumes and a high ratio of monounsaturated to saturated fats, the study found.

Ends