The DSM-IV, diagnostic manual used by mental health professionals in the United States, contains a set of diagnoses called personality disorders that are applied to people with long-term maladaptive patterns of thinking and behaving.  Many of the labels are well known: aranoid, hysterical, psychopathic, narcissistic, and, yes, obsessive-compulsive.

You probably recognize what obsessive-compulsive personality disorder is like.  It is represents the extreme of what in general parlance is referred to as  “obsessive-compulsive” behavior.  It describes the person who is perfectionistic, punctual, aloof, and inflexible.  When severe, obsessive-compulsive personality results in a sort of malignant fussiness: one patient of mine timed family members every time they showered, yelled when anyone put a fork in the dishwasher with the prongs facing down, and insisted on saving the carpet by having family members walk up and down the stairs on newspapers.

The unquestioned assumption among mental health professionals has been, until fairly recently, that obsessive-compulsive personality directly leads to obsessive-compulsive disorder.  That is why, of course, they were both referred to as  “obsessive-compulsive” in the first place. The two disorders were thought to simply represent different levels of severity of the same basic problem; the rigidity and inflexibility of obsessive-compulsive personality was thought to cause by unconscious mechanisms the obsessions and compulsions of OCD.  When I was in training there was no doubt about this link.  Yet although this theory is still cited in newspapers and magazines, the fact is that experts in the field no longer believe it.

First of all, researchers have discovered that obsessive-compulsive personality is not, after all, a necessary condition for the development of OCD.  One study from Harvard University found that only six percent of OCD patients had obsessive-compulsive personality disorder. Perfectionism, studies do suggest, is related to OCD; but the aloofness, or emotional coldness which characterizes the obsessive-compulsive personality is not.   A 1993 study by Russell Noyes and colleagues at the University of Iowa found that the most common personality disorder among OCD patients, present in more than half, is dependent personality disorder–fear of decisions, under assertiveness, and excessive leaning on others.  This finding agrees with what is found in clinical practice: instead being detached as are people with obsessive-compulsive personality disorder, OCD patients are nervous and clinging.

Secondly, the idea that OCD is caused by any personality disorder has been called into question.  In a 1992 study at Harvard, Michael Jenike and his colleagues looked at 17 patients who were diagnosed as having both OCD and personality disorders.  Ten of these patients responded well to medications and behavioral therapy for their obsessions, and when tested again after treatment, nine of the ten no longer had their personality disorders.  What these findings suggest is that when people with OCD have personality disorders, it may well be the obsessions and compulsions that are causing the personality problems, not the other way around.