Eating disorders are classified as Axis Idisorders in the Diagnostic and Statistical Manual of Mental Health Disorders (DSM-IV). Published by The American Psychiatric Association. There are various other psychological issues that may factor into eating disorders, some fulfill the criteria for a separate Axis I diagnosis or a personality disorder which is coded Axis II and thus are considered comorbid to the diagnosed eating disorder. Axis II disorders are subtyped into 3 "clusters", A,B and C.The causality between personality and eating disorders has yet to be fully established.
Some people have a previous disorder which may increase their vulnerability to developing an eating disorder. Some develop them afterwards. The severity and type of eating disorder symptoms have been shown to affect comorbidity.