Comorbidity: Can I Have More Than One Diagnosis?

I ask about family history of mental health as part of a usual assessment. “Mate, my brother has had it all!” Said Graham*, 42. “Started with ADD** as a kid, then got ODD when he was a teenager. Now he’s got a bit of depression, a bit of anxiety and BPD, but he reckons he’s got PTSD‡‡ and he’s also been addicted to at least 3 different drugs!” Graham’s poor brother certainly has had a severe mental health history, experiencing multiple symptoms over the course of his life. However, this doesn’t mean that it’s right to say that he has had 6-8 different conditions.

It’s not uncommon for me to meet or hear about people who have been given multiple psychological diagnoses. Like Graham, many people see psychological diagnoses like physical body diagnoses. You can have a back injury, a heart condition and gastrointestinal issues, and all three might best be viewed as separate conditions. These three problems have a separate cause and are maintained by separate processes. In contrast, the gaps between different psychological disorders are less clearly delineated.

The overlap in psychological diagnoses has been highlighted recently by an international study by authors from Harvard University and MIT published in the journal Science. Using an enormous sample of over 1 million participants, the authors reviewed the genomes (genetic profiles) of people with and without 25 common psychiatric and neurological diagnoses. The authors found that the psychiatric disorders, but not the neurological conditions, have molecular-level similarities. These similarities are not reflected in current diagnostic criteria for mental health diagnoses.

The authors found that some disorders were more in-common than others. They found widespread connections between Attention-Deficit/Hyperactivity Disorder (ADHD), bipolar disorder, major depressive disorder and schizophrenia. Interestingly, some of these conditions, like schizophrenia and depression are in different categories of disorders: schizophrenia is a psychotic disorder and depression is a mood disorder. Similarly, they also found strong genetic overlap between Anorexia Nervosa, an eating disorder, and Obsessive-Compulsive Disorder (OCD), an anxiety disorder.

What does this mean? If I have ADHD does this mean I’ll soon have schizophrenia? Thankfully, having one condition is no great sign that you will contract another. More likely, it means that similar genetic factors influence these conditions. You could imagine that there might be two identical twins, separated at birth and raised in different environments. The life experiences of one child might lead her to develop anorexia. The other might be diagnosed with OCD, or no condition at all. Genetics, upbringing and lifestyle factors can all contribute to mental health symptoms and the presentation of diagnoses.

All of this is not to say that psychological disorders are not real. These disorders do exist, as anyone who has experienced them or worked with people who have them can attest. It is more correct to say that the categories that we currently use are constellations of symptoms that often co-occur. They can help therapists to decide on evidence-based treatments. They can make it easier to do research. But, just like every individual is different, every mental health condition is slightly different. Some are simpler. Some are more complex. Some can neatly be summarised with one label. Others require several labels. Some stay stable over time. Some look different at different times of life.

What does this mean for someone like Graham’s brother? Why six or seven diagnoses? Why did these change over time? I don’t know, I never met him. But perhaps he had an impulsive and emotionally sensitive temperament by nature. Maybe, because of this, he was recognised as a “difficult child” by parents and teachers. To deal with this disapproval he developed avoidant coping methods: he avoided school and used drugs and alcohol. Perhaps the combination of drug use, invalidating home and school environment and underlying emotional sensitivity set off a mood disorder.

When we ourselves have a knot of diagnoses it can feel overwhelming and disempowering. It can feel that we have not one battle to fight against mental health, but several, against each individual condition. If you are in such a situation, it may be helpful to remember that these conditions are probably part of the same problem. And, being part of the same problem, working on making any one thing better will likely make all of them better in time.



* Not real name. Key details changed to protect anonymity.

** Attention-Deficit Disorder

‡ Borderline Personality Disorder (or possible Bipolar Disorder, I didn’t ask for clarification)

‡‡ Post-traumatic Stress Disorder

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