Depression is too widespread a phenomenon for it to be linked in anyway to having thal, study on any sample of population in the world would turn up some depression. Statistics show that almost every human being will go through a phase of depression some time in their life.
Now, when it becomes medically worrisome is if; 1) the depression goes on for too long(over 6 months); 2) starts disabling the person; 3) there may be no known explanation for the depression even to the person themself.
Depression with no explainable or obvious causes, often requires treatment by psychiatrists because it may be due to chemical and hormonal imbalances requiring medication.
The kinds of depression felt by thals, unless they fall in the above-mentioned categories, do not require psychiatric treatment but counseling is always a good idea.
Psychological counseling is, to begin with very much a necessity in fact for parents of infants/young thals. However, rather than by psychologists we notice that thal support groups, other experienced parents of thals, doctors who are thal specialists are the best suited to help them.
The attitude of parents I would say, is the single most imp. foundational factor of the attitude in the thals as they are growing up.
At this point, I must mention that I find a lot of negative attitude in many parents I have talked with esp from rural areas. This is due to the tremendous amount of financial burden they face, with no financial or any kind of aid whatsoever from the government. This is a very different kind of depression I come across with thals and their families, due to the varying standard of medical treament and financial burdens faced by the thals in India. Everything is (so) totally and completely left on the parents of the thals to handle on their own. Thankfully,the standard of treatment and knowledge amongst doctors has shown a great improvement from couple decades ago. There are so many parents as yet who are unable to afford even filters during blood transfusion for their children. While in many developed countries the filtration of the blood is done at source of collection itself, which removes/reduces blood reactions immensely. When the parents have to see their kids suffer more than is required by any thal in many a place in the world, - like regularly having reactions during blood transfusions...I would wonder, who in the world, would not get depressed ? [there are differences in the struggles faced by thals, geographically: and this I will try and post about later].
As Andy said, anemia when the hb is low often causes depression, lethargy and apathy which unfortunately some 'non-thals'assume' to be laziness.....lol So,this is a vast topic...could write a book on it.
Thals also have multiple thal-related probs and complications..one of them being diabetes. There is a medically proven connection between depression and diabetes.
My phase of depression was when my medical reports showed a severe case of osteoporosis which later turned out to be osteopenia. (It was my childhood fear revisited, because I had fractured the same leg thrice during junior years of school. Missed a grt deal of school work of course, but somehow managed to stand first in class that year, first grade.)
Although,the psychosocial issues that are faced by thals all over the world, as outlined by Andy are just as imperative to be understood and need to be addressed.
Bottomline of it though, I'll say that ALL thals,their parents, are such warriors, such courageous people that I think we are like the Spartans................we do not think so much of the outcome of our battle in life, but we all will fight to the death. When I think of the courage we all have, I feel we can teach any people in the world how 'NOT to be depressed'. People derive courage and inspiration from us and feel silly to whine or complain, and I always smile when I hear this from anyone.