The diagnosis of all mental disorders is largely based on a carefully taken history designed to bring out signs and symptoms that, when grouped together, constitute a recognizable syndrome. The problem of diagnosis in mental health arises from the remarkable overlap of symptoms among conditions. Our current method of naming mental disorders, the DSM-IV, has 295 separately named disorders but only 167 symptoms. Consequently, overlap and sharing of symptoms among disorders is common.
To complicate matters further, ADHD is highly comorbid; that is, it is commonly found co-existing with other mental and physical disorders. A recent review of adults at the time they were diagnosed with ADHD demonstrated that 42 percent also had another active major psychiatric disorder. Thirty-eight percent (in other words, virtually all of them) had two or more other mental disorders active at the time they were diagnosed with ADHD. Therefore, the diagnostic question is not, "Is it one or the other?" but rather "Is it both?"
Perhaps the most difficult differential diagnosis to make is that of ADHD versus Bipolar Mood Disorder (BMD). Both of these disorders share primary features:
- mood instability
- bursts if energy and restlessness
- "racing thoughts"
- impaired judgment
- a chronic course
- lifelong impairment
- a strong genetic clustering
In adults the two disorders commonly occur together. Recent estimates find that 15 to 17 percent of persons with BMD also have ADHD. Conversely, 6 to 7 percent of people with ADHD also have BMD (10 times the prevalence found in the general population). Unless care is taken during the diagnostic assessment there is a substantial risk of either misdiagnosis or of a missed diagnosis. Nonetheless, a few key pieces of history can guide us to an accurate diagnosis.
Affect is a technical term that means the level or intensity of mood. By definition then an affective or mood disorder is a disorder of the level or intensity of an individual's mood. The quality of mood (happy, sad, irritable, hopeless) is readily recognizable by everyone. What makes it a disorder are two other factors.
First, the moods are intense, either high energy (called mania) or low energy (called depression). Secondly, the moods take on a life of their own unrelated to the events of the person's life and outside their conscious will and control. Although some environmental triggers have been identified for episodes of mood disorders, usually the abnormal moods gradually shift for no apparent reason over a period of days to weeks and persist for weeks to months. Commonly, there are periods of months to years during which the individual is essentially back to normal and experiences no impairment. Although we now are doing a much better job of recognizing that children can and do have all types of mood disorders, the majority of people develop their first episode of affective illness after the age of 18.
This is a highly genetic neuro-psychiatric disorder characterized by high levels of inattention/distractibility and/or high impulsivity/physical restlessness that are significantly greater than would be expected in a person of similar age and developmental attainment. To make the diagnosis of ADHD this triad of distractibility, impulsivity and (sometimes) restlessness must be consistently present and impairing throughout the lifespan. ADHD is about ten times more common than bipolar mood disorder in the general population.
The two disorders can be distinguished from one another on the basis of six factors:
1. Age of Onset: ADHD symptoms are present lifelong. The current nomenclature requires that the symptoms must be present (although not necessarily impairing) by seven years of age. BMD can be present in prepubertal children but this is so rare that some investigators say it does not occur.
2. Consistency of Impairment and Symptoms: ADHD is always present. BMD comes in episodes that ultimately remit to more or less normal mood levels.
3. Triggered Mood instability: People with ADHD are passionate people who have strong emotional reactions to the events of their lives. However, it is precisely this clear triggering of mood shifts that distinguishes ADHD from Bipolar mood shifts that come and go without any connection to life events. In addition, there is mood congruency in ADHD, that is, the mood reaction is appropriate in kind to the trigger. Happy events in the lives of ADHD individuals result in intensely happy and excited states of mood. Unhappy events and especially the experience of being rejected, criticized or teased elicit intense dysphoric states. This "rejection sensitive dysphoria" is one of the causes for the misdiagnosis of "borderline personality disorder".