The link below is to a piece I wrote for a Sports Law site called LegalBall.com a few years ago, right after Pantani died. I just re-read it and considering the current doping issues in all sports (not just cycling) I thought it was relevant...although somewhat dated. I am becoming more educated on the psychological effects of performance enhancing drug use and believe that we are just beginning to uncover the long-term damage to brain chemical and hormonal ratios that can result. The piece below deals largely with cardiovascular issues but in retrospect, I think it scratches the surface and hints at the psychological effects as well.
It is not uncommon for many ex-professional athletes to suffer from serious depression after their careers, even if they have not used PED's. Especially in a sport as universally demanding as cycling. The potential psychological reasons for this are numerous however, if we apply any basic principles of physiological adaptation to the equation, we must acknowledge the potential long-term effects of external hormonal or chemical influences capable of altering internal functions to the degree that performance is enhanced.
In short: Even as a "clean" athlete you are at a risk of post-career depression and psychological issues simply as a result of your habits and unconscious sense of self after many years of competition. Regular, habitual or even random hormonal or chemical influences during ones career can likely enhance any prior disposition for these future problems. Marco would probably agree...if he could.