I don't feel unfulfilled as much as I feel out of control. I tend to think of anxiety and especially HA as something that arises from the need for control or the fear about not being in control. If you read each of the entries so far it appears that anxiety often reared its head when people had something happen that they were unhappy with but felt like they couldn't control. And health, and anxiety symptoms are things that really aren't in our control but we like to think it is - so we try to control it.
My anxiety didn't start until my early 30s when I started to have children. I know I'm a control freak - always have been. Before kids I'd always been able to control much of my life - by working hard I got into every college and grad school I applied to, I've gotten every job I wanted, I've always been healthy, I've been happy with my friends, I've never really had big traumas in my life. But as soon as I had kids I realized: (1) I have massive responsibility thus I need to truly be in control (2) with kids you sort of don't have control over things, especially when they are babies (they don't sleep well, they don't always eat well, when they're sick they can't tell you what's wrong, etc) (3) the possibility of screwing up is unbearable because I love these little beings so intensely that I want their lives to be perfect! (impossible, obviously!)
In the course of my anxiety and raising children (mine are now 4 & 7) I think I've actually found more meaning in my life. But my anxiety is not gone. I think any trauma, including facing anxiety, forces you to do some soul searching and, obviously, change your life. The whole ordeal hasn't made me lose my religious faith. On the contrary I think there is a purpose to my anxiety in that I think it's helping me to grow, to understand myself much better than I ever have before and deepen my faith. I've never had anything happen in my life where I had to sit back and think about how I was living, handling stressors, treating my body, etc. So my body decided to send out warning signals (anxiety symptoms) to let me know, in no uncertain terms, that it was time to change. So here I am.
One note that might pertain here, my mom has suffered from health anxiety for over 30 years. It's much, much better for her now than it was in her younger years. One of her little "sayings" when I call and talk to her about how my anxiety is pretty bad that hour/day/week she'll say: when you can't help yourself, force yourself to go out and help someone else. You'll all benefit. If you look at her life you'll see how that's filled her life with meaning. It's hard to do, but good advice. I think often having HA we're all too inwardly focused and it's to our detriment.
Finally, I don't know if serotonin imbalance causes HA but I do know that SSRIs can help. I took Celexa for 9 months and felt great. Went off it to get pregnant and the anxiety crept back several months later. Now 2 years later I started back on Celexa 7 weeks ago and I think it's beginning to work. There is clinical evidence that this may work. I know of one current study going on being run by a former psychiatrist of mine, Dr Arthur Barsky, director of psychiatric research at Brigham & Women's hospital. There is at least one person on this board that is participating in the study - run out of Boston & NY. The study is an NIH funded study investigating the impact of SSRIs on HA. Half the group gets cognitive behavioral therapy and prozac. The other half gets just the therapy and a placebo. You can see the info about it here:
http://www.thehealthstudy.com and the first video at
http://www.thehealthstudy.com/hypo-participate.html shows the psychiatrists talking about what helps hypochondria (including SSRIs) It will be interesting to see the outcome of the study.