Having more than one psychiatric diagnosis is more common than you think. This is why it matters.

Having two or more psychiatric diagnoses at the same time occurs for at least half of those diagnosed with a mental illness. As with other illnesses, it’s important to understand the full picture to find the best treatment.

psychiatric comorbidity, psychiatry in Canada
If you don’t have the right diagnosis, you won’t find the best treatment for your unique needs. Because there are no objective tests in psychiatry (e.g., lab test or brain scan to confirm a diagnosis), finding the best medication already requires trial and error.

Lisa’s family doctor diagnosed her with depression but her symptoms didn’t improve with the prescribed antidepressant. Her doctor had her complete some questionnaires that confirmed the depression diagnosis and also determined Lisa had an anxiety disorder, so her doctor suggested she increase the antidepressant dose. Lisa shared this information with her best friend who expressed a strong opinion, stating, “I think you’re being over-medicated. How do you go to your doctor with one diagnosis and leave with two? Are you sure she knows what she’s doing?”

Lisa had started to feel much better soon after her antidepressant dose was increased, but her friend’s comments made her second guess herself and her doctor, so she stopped the antidepressant.  Within weeks, her mood and anxiety were much worse, so Lisa went to her local emergency room, where she waited for 12 hours before being assessed. “It was a terrible experience,” Lisa recalled. “I wish I had stuck to the plan I made with my doctor, but I also wish I didn’t need medication at all.”

This fictional story is incredibly common and it speaks to the lack of knowledge regarding the importance of correctly diagnosing and fully treating the symptoms of a mental illness. In this blog, I will unpack the concerns raised by Lisa’s friend and explain why her family doctor ultimately gave her the correct advice.

Psychiatric comorbidity is the rule, not the exception

Psychiatric comorbidity – to have two or more psychiatric diagnoses at the same time – occurs for at least half of those diagnosed with a mental illness. 

While Lisa’s friend expressed shock about her having two psychiatric diagnoses at the same time, this is actually pretty much the norm with many illnesses! High cholesterol, diabetes and hypertension commonly co-occur and we don’t ignore any one of them because it seems like too many diagnoses – we know it’s important to treat every disorder to avoid a serious outcome, like a heart attack or stroke. Psychiatric illnesses are no different. 

The most common psychiatric comorbidity is major depressive disorder (MDD) co-occurring with an anxiety disorder.  About 85% of people diagnosed with MDD have anxiety symptoms. Sometimes, those anxiety symptoms are so consistent, persistent, and impairing that they are referred to as an anxiety disorder.

Anxiety disorders include generalized anxiety disorder, panic disorder and social anxiety disorder. While the DSM-5 no longer categorizes obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD) as anxiety disorders, both are associated with significant anxiety and both commonly co-occur with MDD.

At some time during their illness, 90% of people diagnosed with an anxiety disorder will have comorbid MDD.  

For bipolar disorder (BD), comorbidity is the rule. Studies have found that nearly 70% per cent of people with BD have at least one comorbid psychiatric diagnosis, most frequently anxiety disorders, substance use disorders and ADHD.

Correct diagnosis is essential

Here are the top reasons why the correct diagnosis, including identifying comorbid conditions, is essential.

  1. You want the right treatment: If you don’t have the right diagnosis, you won’t find the best treatment for your unique needs. Because there are no objective tests in psychiatry (e.g. lab test or brain scan to confirm a diagnosis), finding the best medication already requires trial and error. Without fully understanding all of the diagnoses, finding the right treatment quickly is far less likely.
  2. Treatment-resistance: Comorbidity makes recovery more difficult because it adds complexity. Treatment-resistance, which means symptoms don’t respond to usual treatments at usual doses, is more likely when there are unrecognized and therefore untreated or undertreated comorbid disorders.
  3. Greater burden of illness: Comorbidity has been associated with longer illness episodes, worsening cognitive symptoms, greater functional impairment and increased suicide risk. The identification and appropriate treatment of all diagnoses reduces that risk.
  4. Comorbidity requires treatment adaptations: When MDD and anxiety co-occur, higher antidepressant doses are often required and anxiety symptoms commonly take longer to respond to treatment. Additionally, some antidepressants are better at managing anxiety symptoms than others. When bipolar disorder is associated with an anxiety disorder or ADHD, the treatment approach must be adapted to avoid making the mood more unstable. However, failing to address those comorbid disorders can have terrible consequences: more suffering, more functional impairment and greater suicide risk.   
  5. The earlier the better: Determining the right diagnosis close to the time of symptom onset has many benefits.
    1. Appropriate treatment can be started sooner, which increases the likelihood of it working effectively.
    2. The longer a mental illness is untreated, the more harm it can cause – that includes prolonging/ deepening personal suffering, financial impacts and social challenges, but also the negative effects of untreated or under-treated illness on the structure and function of the brain. These brain changes can lead to treatment-resistance and a greater burden of illness.
    3. Treating an illness early and fully reduces the risk of developing a comorbid condition. If comorbidity is already present, early diagnosis and treatment improve the likelihood of treatment response and full recovery.

Being properly informed matters

Lisa’s doctor gave her the best possible guidance by identifying not only the depression but also a comorbid anxiety disorder. Fortunately, antidepressants are prescribed for both anxiety and depression symptoms, when they are distressing and significantly impact an individual’s functioning in their usual roles (e.g., at home, work, school or socially).

By choosing an antidepressant that helps depression and anxiety symptoms and increasing the dose when her symptoms didn’t fully resolve, Lisa quickly started to feel better.

However well-meaning, by undermining Lisa’s confidence in herself and her doctor, her friend’s uninformed comments had a seriously detrimental impact on Lisa’s health, prolonging her journey towards recovery.

Dr. Diane McIntosh is a psychiatrist, innovator, educator, author and speaker. She is a passionate advocate for better mental health care, and a champion for all who suffer from mental health challenges. 

See Diane’s other posts on choosing medication. 

This blog post is part of a series looking at the state of our mental healthcare system and ways we can create sustainable change to improve quality and outcomes for anyone impacted by mental illness. 

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Dr. Diane McIntosh

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Dr. Diane McIntosh is a psychiatrist, innovator, educator, author, and speaker. She is passionate advocate for better mental health care, and a champion for all who suffer from mental health challenges.

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