When an individual has two or more distinct illnesses at the same time, this is called comorbidity. The ailments could be physical or mental. For example, a person might suffer from depression and multiple sclerosis, or anxiety and an eating disorder.
Disease overlap is common. Historically, 80 percent of Medicare spending covers patients with four or more concurrent conditions. Multiple disorders can exacerbate one another and make treatment a longer process or more difficult to achieve.
Many different mental health disorders can co-occur. One common example is depression and anxiety. However, some researchers argue that the two have similar roots and therefore do not constitute distinct disorders. Nonetheless, depression commonly overlaps with other disorders as well, such as bipolar disorder and ADHD.
Illness can bring worry as well as racing thoughts, and this repetitive thinking can bring on sleep difficulties. In fact, insomnia and other conditions seem to go hand in hand for many people. One of the most common combinations is insomnia and depression. However, just a few sessions of talk therapy, such as cognitive-behavioral therapy for insomnia, can help on both fronts, addressing insomnia and depression. In fact, lifting insomnia will help lift depression.
• Obsessive-compulsive disorder: Disorders including mood, anxiety, somatoform, hypochondriasis, body dysmorphia, impulse control, eating disorders.
• Insomnia: Disorders include substance use, anxiety, mood disorders.
• Narcissistic personality disorder: Disorders including antisocial, histrionic, borderline, schizotypal, and passive-aggressiveness.
• Obesity: Diabetes, stroke, cardiovascular disease, hypertension, sleep problems, mood disorders.
• Cancer: hypertension, hyperlipidemia, osteoarthritis, hypothyroidism, diabetes mellitus, coronary artery disease, mood disorders.
• Multiple sclerosis: Mood disorders, anxiety, hypertension, hyperlipidemia, and chronic lung disease.
• Arthritis: Diabetes, heart disease, obesity, mood disorders.
• Cardiovascular disease: Cancer, diabetes, back and neck problems, osteoarthritis, chronic obstructive pulmonary disease, vision problems.
The combination of substance use disorders and other mental illnesses is widespread. Half of the people who experience a mental illness will also be diagnosed with a substance use disorder at some point in their lives, according to the National Institute on Drug Abuse. The same goes for those first diagnosed with a substance use disorder and later a mental illness. In 2018, 9.2 million Americans had both a substance use disorder and a mental illness, according to the National Survey on Drug Use and Health.
A person can be first diagnosed with either a substance use disorder or a mental illness. Sometimes they occur concurrently, or they can occur one after the other.
Two categories can overlap for a few reasons. The same genetic or environmental factors could increase the risk of developing multiple disorders. There’s also evidence that the development of some mental disorders can render the individual more vulnerable to a substance use disorder and vice versa.
Treatment should center around all the presenting conditions, rather than treating one in isolation. Successful treatment may leverage medications, such as buprenorphine, and behavioral therapies, such as cognitive-behavioral therapy or dialectical behavior therapy.
Continuing research on the relationship between different diseases is critical to developing the most effective treatment approaches. On an individual level, disclosing multiple disorders to a physician is key to achieving successful care.