Eating fast foods such as hamburgers, hotdogs and pizza and baked commercial goods like fairy cakes, croissants and doughnuts is linked directly to depression, it has been confirmed.
The study, headed by scientists from the University of Las Palmas de Gran Canaria and the University of Granada, found that fast food consumers, compared to those who eat little or none, are 51% more likely to develop depression.
Published in the Public Health Nutrition journal, the results also found the more fast food consumed, the greater the risk of depression.
The study demonstrates that those participants who eat the most fast food and commercial baked goods are more likely to be single, less active and have poor dietary habits, which include eating less fruit, nuts, fish, vegetables and olive oil. Smoking and working more than 45 hours per week are other prevalent characteristics of this group.
Of commercial baked goods, Almudena Sánchez-Villegas, lead author of the study, said: "Even eating small quantities is linked to a significantly higher chance of developing depression,"
The study sample belonged to the SUN Project (University of Navarra Diet and Lifestyle Tracking Program). It consisted of 8,964 participants that had never been diagnosed with depression or taken antidepressants. They were assessed for an average of six months, and 493 were diagnosed with depression or started to take antidepressants.
This new data supports the results of the SUN project in 2011, which were published in the PLoS One journal.
The project recorded 657 new cases of depression out of the 12,059 people analysed over more than six months. A 42% increase in the risk associated with fast food was found, which is lower than that found in the current study.
Sánchez-Villegas concludes that "although more studies are necessary, the intake of this type of food should be controlled because of its implications on both health (obesity, cardiovascular diseases) and mental well-being."
Depression affects 121 million people worldwide. This figure makes it one of the main global causes of disability-adjusted life year. Further still, in countries with low and medium income it is the leading cause.
However, little is known about the role that diet plays in developing depressive disorders. Previous studies suggest that certain nutrients have a preventative role. These include group B vitamins, omega-3 fatty acids and olive oil. Furthermore, a healthy diet such as that enjoyed in the Mediterranean has been linked to a lower risk of developing depression.