Michael Jackson's previous doctors and lawyers are saying that he suffered from an eating disorder such as anorexia. (Anorexia is listed as a mental illness.) Jackson was also viewed as very controlling, particularly with his image, and there is speculation that an underlying condition (obsessive compulsive disorder) may have given rise to eating disorders.
One explanation suggested for his many plastic surgeries is "Body Dysmorphic Disorder", a severe distortion in how one views his or her body.
Jackson and his brothers and sisters have publicly commented on the physical punishment meted out by his father Joe Jackson when the siblings were younger. This is suggested as another possible cause for many of Michael's later idiosyncrasies.