One of the tricky things about mental illnesses is that they rarely exist on their own. Not only are they a complicated combination of different causes and symptoms, having one mental illness doesn’t exclude you from having others at the same time. That can make both diagnosis and treatment a lot more difficult.
Diseases that occur at the same time are called comorbidities, and it might not be a surprise to learn that depression is particularly prone to sharing headspace with other mental illnesses (and some physical ones as well) (https://bmcpsychiatry.biomedcentral.com/articles/10.1186/s12888-020-02546-8). After all, when you’re not well, it’s natural for your mood to be lower, and it’s much harder to take steps to combat it. That can easily slip over into the clinical definition of depression.
People with a major depressive disorder quite often also have some kind of anxiety disorder as well. They may experience problems with substance abuse. That doesn’t just mean illegal drugs, with alcohol and tobacco smoking at the top of the list. Some may have personality disorders, which includes things like borderline personality disorder and antisocial personality disorder. More serious conditions may be schizophrenia or bipolar disorder.
Sometimes these conditions existing at the same time may be a coincidence. Other times, they may impact each other. They’re also going to affect your treatment options. Substance abuse disorders in particular may influence the kinds of prescribed medication you can take or how effective it will be.
If you’re facing a major physical illness like heart disease or cancer or even trying to manage more common conditions like high blood pressure or diabetes, depression is considered a risk factor that could make your long-term outcomes worse. It just makes everything more challenging.
This doesn’t just have implications for your mental and physical health. It makes things a lot more expensive for both you and society as a whole. When trying to manage depression, you need to consider comorbidities, and when treating other conditions, you need to be aware of the risks that depression poses.
Lots of scientific research has been done and will probably continue to be done regarding comorbidities for depression. By learning more about how different diseases, both mental and physical, interact, we might be able to improve outcomes for everyone involved. Just be aware of how complicated it can all be.
