- the fairly common occurrence of more than one diagnosis at the same time in the same patient, and
- the similarities and overlapping symptoms of many psychiatric disorders, making it difficult to make a clear distinction or choose appropriate treatment methods.
These difficulties may arise because of inadequate definitions for disorders. We don’t have biological markers for any of these disorders. The criteria used are based on expert consensus and may not reflect true biological boundaries between conditions.
Mental disorders related to multiple genes
Experts believe most psychiatric disorders are related to multiple genes as well as environmental influences. Each of the multiple genes may have several variants. The combination of variants present as well as the differing environmental influences in an individual’s life may determine the pattern of symptoms present and could account for multiple diagnoses.
Depressed patients are extremely likely to also meet diagnostic criteria for 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 per cent 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.
These three disorders 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 the wrong disorder has been diagnosed, the reason for the ineffectiveness of medication may not be evident to the physician.
Little research in multiple mental disorders
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. As the biological basis of these symptoms becomes better understood it is likely that our diagnostic system will evolve to reflect this.
Dr. Latimer is president of Okanagan Clinical Trials and a Kelowna psychiatrist.
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