Overlap between disorders

One of the difficulties in the diagnosis and treatment of mental illness is the fairly common occurrence of more than one disorder at the same time in the same patient. Also, the similarities and overlapping symptoms of many psychiatric disorders can make it difficult to make a clear distinction or choose appropriate treatment methods.

This difficulty may arise because of inadequate definitions for disorders or because the conditions involve multiple genes. In that case, the nature of the symptoms could depend on the combination of genes present in a specific patient. This is quite possible as we are learning that most psychiatric disorders are not due to a single gene.

A very large number of people suffering from one psychiatric illness also experience one or more other disorders. For example, depressed patients are extremely likely to also have an anxiety disorder and those with attention deficit/hyperactivity disorder (ADD/ADHD) often also develop bipolar disorder during their lifetime.

Sometimes, co-occurring disorders can be effectively treated with only one medication as is the case with depression and anxiety, but with other disorders it is not such a simple problem.

An excellent example is the common overlap between borderline personality disorder, bipolar disorder and ADD/ADHD. These three disorders in particular are frequently found to co-exist. Some research suggests that as many as 30% of people with childhood ADD/ADHD will develop bipolar disorder. Borderline personality disorder is also commonly found in conjunction with both ADD/ADHD and bipolar disorder.

At least one expert has gone so far as to suggest that borderline personality disorder does not actually exist and is simply undiagnosed bipolar disorder because of the frequency with which the two occur together or overlap in symptoms. This belief is not widely held in medical circles, but is an example of just how related these two conditions can be.

Not only do the three disorders sometimes exist at the same time in a person, but they can be difficult to distinguish from each other because of many overlapping symptoms. All three conditions exhibit symptoms such as moodiness, poor impulse control, irritability, relationship difficulties, poor educational and job performance and frequent alcohol and drug abuse. The presence of drug or alcohol abuse may make diagnosis impossible in the short term.

Unfortunately, medications for one disorder can often make another worse. For example, while stimulant medication such as Ritalin or Dexedrine are effective for treating the symptoms associated with ADD/ADHD, the same drug can trigger a manic or mixed mood episode in a bipolar patient. Likewise, while mood stabilizers will help bipolar disorder patients and some borderline patients, they will do nothing for ADD/ADHD. Antidepressants may help depression, but can lead to mood swings or mania in patients who are bipolar.

If only one disorder has been diagnosed in that patient, or if the wrong disorder has been diagnosed, the reason for the ineffectiveness of medication may not be evident to the physician.

In the case of co-existing bipolar disorder, borderline personality disorder and/or ADD/ADHD, combinations of medications can be necessary for effective treatment and that is why it is important for physicians to thoroughly screen for all conditions.

Considering the overlap and the frequency with which these conditions are found together in the same person, it is likely that there are genetic links between them. However, very little research has been done on these overlaps at this time and the biological basis for these links is not fully understood. Continued research into this possibility could lead to a greater understanding of these psychiatric conditions and to more effective treatments in the future.


Current Studies

 Alzheimer's Disease 


 Parkinson's Disease





 Interested in participating? Call us for more information!