By Mary Fetzer
Clinically reviewed by Dr. Raafia Muhammad, MD, MPH
Experts believe half or more of people with ADHD also suffer from one or more accompanying conditions — what are called “comorbidities.”
Most often, these accompanying conditions are mental health disorders or conditions.
Researchers in Sweden accessed the health records of their country’s entire population, which enabled them to identify and quantify psychiatric and medical disorders. Their 2018 study, published in PLOS ONE, looked at the records of 5.5 million adults aged 18 to 64. Among them were the 1% who were diagnosed with ADHD at some point in their adult lives.
The study compared adults with ADHD and adults not diagnosed with ADHD and found that individuals with ADHD were 20 times more likely to be diagnosed with bipolar disorder and nine times more likely to suffer from depression, anxiety disorder, or substance use disorder than the non-ADHD population. (The study noted that more than 80 percent of those with ADHD had been prescribed medication for their ADHD, but it’s not clear whether that medication was prescribed before they were diagnosed with the other conditions.)
The differences were even greater among older adults, according to the Swedish study. Although ADHD was less than a third as prevalent in the over-50 population as in the general adult population, this older group was 23 times more likely than their non-ADHD peers to be diagnosed with bipolar disorder and 12 times more likely to suffer from depression, anxiety, or substance abuse.
“People with ADHD have been found to have a higher likelihood than the general population of developing comorbidities,” says Kate Hanselman, a psychiatric mental health nurse practitioner at Thriveworks, an online membership-based mental health
practice based in Stamford, Connecticut. Hanselman is also living with ADHD.
ADHD and Other Psychiatric Conditions
Psychiatric conditions commonly co-occur in adults with ADHD, especially mood and anxiety disorders, substance use disorders and personality disorders, according to a 2017 research study in the journal BMC Psychiatry. The overlapping symptoms of these psychiatric comorbidities can complicate the recognition, diagnosis and treatment of ADHD.
ADHD and Bipolar Disorder
ADHD has a high prevalence of comorbidity with bipolar disorder, according to the BMC Psychiatry study. Overlapping characteristics include restlessness, talkativeness, distractibility and fidgeting. To differentiate bipolar disorder and ADHD for the purpose of diagnosis and management, mental health professionals look for the distinctive features of bipolar disorder, especially the depressive phase of bipolar when the person has a significanty depressed mood or loss of interest in activities.
A 2008 study in the European Archives of Psychiatry and Clinical Neuroscience, said studies have shown that 9% to 21% of people with bipolar disorder also have ADHD, and that 5% to 47% of people with ADHD also have bipolar disorder.
Studies suggest that the onset of bipolar disorder occurs at an earlier age in individuals with ADHD. Also, bipolar individuals with comorbid ADHD demonstrated worse overall illness, with shorter periods of wellness, more frequent episodes of mania and depression, and higher instances of additional comorbid psychiatric conditions, according to the 2008 study. Those other comorbid conditions included anxiety and substance abuse disorders.
ADHD and Depression
The rate of depression in individuals with ADHD has been found to range from 18% to as high as 53%. The National Comorbidity Survey, a nationally representative community household survey of the prevalence and correlates of mental disorders in the U.S., conducted in 1992 and again in 2002, pegged the figure at 18.6%. A 2006 study in the Nordic Journal of Psychiatry found that 53.3% of people it studied also had depressioin. A presentation at the 2016 Anxiety and Depression Association of America Conference revealed that 28% of individuals referred to clinics for mood and anxiety assessments had undetected ADHD.
The studies revealed that individuals with comorbid ADHD and depression have a lower self-reported quality of life than those suffering from depression without comorbid ADHD.
ADHD and Anxiety Disorders
The risk for anxiety disorders is higher in individuals with ADHD than in the general population. About 50% of people with ADHD also suffer from anxiety, according to the National Comorbidity Survey.
People with anxiety disorders who have comorbid ADHD tend to have more severe anxiety symptoms, earlier age of onset of anxiety, and more frequent additional comorbid diagnoses than those who do not have ADHD, according to a 1999 study in the journal Psychological Medicine. Furthermore, ADHD is often diagnosed later in these individuals than it is in people without anxiety. That may be in part because the anxiety inhibits the impulsivity of ADHD.
ADHD and Substance Use Disorder
The most common comorbid condition with ADHD is substance use disorder, or SUD. Substance abuse or dependency — particularly that involving alcohol, nicotine, cannabis, or cocaine — is nearly twice as common in individuals with ADHD as it is in the general population, according to a 2013 study in the International Journal of Adolescent Medicine and Health.
The association between ADHD and substance abuse disorder may involve impulsivity and attempts to self-medicate ADHD symptoms — such as managing mood or sleep — according to a 2011 study in the journal Current Opinion in Psychiatry.
Having ADHD and substance use disorder is associated with earlier onset of substance abuse. Having both is also associated with more hospitalizations, less likelihood of achieving abstinence, lower rates of treatment, and increased likelihood of suicide attempts. Because of all of that, it is important that mental health professionals screen for ADHD in patients with substance abuse disorder, and vice versa.
ADHD and Personality Disorders
There is less research on comorbidity between ADHD and personality disorder. A 2011 study published in the journal Primary Care Companion for CNS Disorders found that personality disorders were present in more than half of adults with ADHD. It also found 27% of individuals with ADHD had two or more personality disorders.
An important takeaway from the study was that individuals with ADHD and personality disorders have more severe impairment and exhibit lower response rates to treatment, compared to adults with ADHD alone.