Dual Diagnosis Info Guide

What is dual diagnosis?

The term dual diagnosis is used to describe a situation where someone has both a developmental disability and a mental health problem.

Developmental disabilities and mental health problems are some- times very hard to tease apart. Family members and treatment professionals often find it difficult to determine whether the behaviour they are looking at is due to an underlying disability or a mental health problem or both.

How common is dual diagnosis?

People with developmental disabilities are at increased risk for developing mental health problems throughout their lives. Large-scale studies indicate that people with developmental disabilities are three to six times more likely to develop a mental health disorder than other people. Estimated rates vary depending on the types of problems included as the “second” diagnosis, but it is clear that many people with developmental disabilities have serious mental health problems:

• Psychotic disorders have been suggested to occur three times more often in adults with developmental disabilities compared to the general population (Cooper et al., 2007; Turner, 1989). Rates of psychotic disorder may be inflated in some studies due to challenges in making the diagnosis, particularly by clinicians with less training in developmental disabilities (Lunsky et al., 2006; Robertson et al., 2000).
• One large study in the U.K. reported that mood disorders (e.g., major depression, bipolar disorder, dysthymia) were three times more common in those with developmental disabilities than in the general population (Richards et al., 2001). Comparative studies have reported higher rates in individuals with developmental disabilities than in the general population.
• Anxiety disorders (e.g., posttraumatic stress disorder, separation anxiety, social phobia, specific phobias, panic disorder, generalised anxiety disorder) are also common in people with developmental disabilities, particularly among those with specific genetic syndromes (Harris, 2006).
• Challenging behaviour sometimes called “disruptive behaviour”

or “problem behaviour,” refers to behaviour that limits the person’s use of ordinary community facilities, or behaviour that, because of its intensity, frequency or duration, puts the physical safety of the person or others at risk (Emerson & Emerson, 1987). The overall prevalence of disruptive behaviour in adults with developmental disabilities has been estimated at 22.5 per cent (Cooper et al., 2007). This behaviour may be due to an underlying psychiatric disorder, but it may also have other causes.

Recognizing Dual Diagnosis

The relationship between developmental disability and mental health problems

The relationship between developmental disabilities and mental health problems is complex. Mental health problems present in unique ways in people with developmental disabilities, and how they present can change over time.

• Various biological, psychological and social factors make it more likely that a person with a developmental disability will develop a mental health problem, compared with someone without a dual diagnosis.
• How mental health problems look can depend on the developmental disability. It can be difficult to understand the inner experience of a person with a developmental disability because they might have difficulty expressing their thoughts and feelings. This makes traditional ways of making a diagnosis challenging because they depend on a person being able to report their inner experience.

Dual diagnosis: An information guide

• It is also hard to make a diagnosis when the behaviour of concern has increased in intensity but is “old” behaviour, meaning that the person has exhibited it for a long time. For example, if a man has always pulled his hair, mostly when he is left alone, but has begun to pull much harder and more often, and not just when he is alone, does this change mean that he has a new mental health problem, or is it just part of the same problem?
• Diagnosing mental health problems in someone with a developmental disability requires information from various sources and from different settings.

Genetic Disorders

Some genetic disorders that cause developmental disability can predispose a person to having specific mental health problems. For example, someone who has fragile X syndrome is at increased risk for developing social anxiety, and someone with 22q11 deletion is at increased risk for developing schizophrenia. This is one reason why it is very important to know the cause of a person’s developmental disability. We did not have the technology 20 years ago to recognize many of the syndromes that we can now identify, so there may be people with dual diagnosis who have a genetic disorder that has not yet been diagnosed.