People who eat fast food - when compared to those that eat none - have a 51% higher depression risk, the scientists found.
There is also a so-called 'dose-response effect' for fast food.
Dr Almudena Sánchez-Villegas, the lead author of the study, explained: "...the more fast food you consume, the greater the risk of depression."
The research showed that those eating the most fast food and commercial baked food were more likely to be:
- less active,
- single,
- smokers,
- working over 45 hours per week.
The study involved 8,964 people who were followed for an average of 6 months. Of these, 493 started taking antidepressants during the study or were diagnosed with depression.
The results are in line with a previous study which found that eating fast food was linked to a 42% increase in depression risk.
Dr Sánchez-Villegas said:
"...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."Certain nutrients are thought to have a preventative effect on depression. These include B vitamins, omega-3 fatty acids and olive oil.
The Mediterranean diet has also been repeatedly linked to lower levels of depression. It is more difficult to get these vital nutrients from fast food.
Comment: Is it any wonder some Russians have called for American fast food corporations to be registered as foreign agents and mandatory warnings and threatening pictures for fast food packaging? And is it any wonder the US has a seriously worsening epidemic of depression when over a third of children and teens eat fast food daily.
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