A group of researchers from Israel has discovered that rats exhibiting the signs of depression have increased levels of the omega-6 fatty acid, arachidonic acid, in their brains.

There is also evidence that depression may be associated with a dietary deficiency in omega-3 fatty acids. This “phospholipid hypothesis” of depression has been supported by research showing that omega-3 fatty acid concentration in the blood of depressed patients is lower than that in control patients.

In the new study, researchers examined the brains of depressed rats and compared them with brains from normal rats. Surprisingly, they found that the main difference between the two types of rats was in omega-6 fatty acid levels and not omega-3 fatty acid levels. Specifically, they discovered that brains from rats with depression had higher concentrations of arachidonic acid, a long-chain unsaturated metabolite of omega-6 fatty acid.

Arachidonic acid is found throughout the body and is essential for the proper functioning of almost every body organ, including the brain. It serves a wide variety of purposes, from being a purely structural element in phospholipids to being involved in signal transduction and being a substrate for a host of derivatives involved in second messenger function.

Although far less attention has been paid to dietary requirements for omega-6 fatty acids, which can be found in most edible oils and meat, perhaps in the future depression may be controlled by increasing omega-3 fatty acid intake and decreasing omega-6 fatty acid intake.

American Society for Biochemistry and Molecular Biology, May 25, 2005