Question: environment can affect seratonin levels to the point of causing depression. Why is seratonin not, therefor, controlled internally to a greater extent so as to give the individual a better chance of coping with the negative environment?

Rachael Ward answered on 13 Jun 2011:

Hi laurenisfabby,

What a great question. That is basically what I want to know!
Youre right, experiements in animals have shown that environment, especially high levels of trauma and anxiety can disrupt levels of serotonin and affect how well the animal can deal with stress, or if they get agressive or socialise well.

There are probably many reasons why the brain can’t deal with this better. Some animals and people may have inherited genes which mean they have less control over how serotonin is released. Also, very subtle differences can occur while your brain is developing, both in the womb and as a baby that might alter the brains ability to control serotonin.

Also, many believe that it is partly due to how quickly the world is changing around us. Human brains have evolved and grown from about 400g 3-4 million years, to their present size of about 1400g so they have grown and changed a lot. However, this is a slow process and has taken millions of years. If you think that “just” 300 years ago, our brains were about the same as they are now but now they have to deal with totally different stresses than those they evolved to cope with before. They were designed to deal with the stress of hunting and gathering food in small groups and families, not of the train being late or the computer breaking or of being surrounded by huge, urban cities! So maybe they simply havent evolved to deal with a lot of these new, negative aspects of our modern environment. That could be where a good drug to restore serotonin levels may be more useful today

This is a tricky question though, please let me know if I’ve answered it okay!