Most people do not look at depression as having any advantages, they see it as an inhibitor. I see depression as both physiological as well as an adaptation. In both the article from Nesse and the one above, depression is said to have benefits. When people are depressed they tend to think about the things that are causing them problems. Depression makes it hard for them to think about anything else; therefore they are more likely to overcome these problems with the right frame of mind. This kind of analysis needs little distraction. Neurons need to fire rapidly to avoid distractions. Studies done on rats show that the 5HT1A receptor helps fuel neurons to fire, and also to keep them from breaking down. Rodents with this receptor have fewer depressive symptoms when introduced to stress. This suggests that the 5HT1A receptor is somehow linked to depression. This helps support the question of whether or not depression is an adaptation. In some cases depression could just be an adaptation to help us analyze and overcome our problems effectively. Some people are more genetically prone to depression though. Medical conditions such as a thyroid disorder, or chemicals in medications and alcohol, play a great role as well.