Depression can increase susceptibility to other diseases like anxiety, substance use disorders, and chronic illnesses. In this post, we will explore how depression interacts with these other conditions.
Depression has often been linked to anxiety disorders, and the two are seen more often together than not. This is important because people with both generally have a poorer response to treatment, more chronic course of illness, increased incidence of suicidal thoughts and attempts, and greater disability. There is no clear evidence suggesting that one causes the other, but the two do share a similar subset of symptoms, including fatigue, sleep disturbance, restlessness, and difficulty concentrating.
This makes it even more important to recognize when the two occur together. After all, not only does co-occurrence result in poorer treatment response, but some medications designed to treat one condition can make the other worse.
Substance use disorders
Studies have found that people with depression also frequently have a substance use disorder. Up to about one-third of people with depression also have an alcohol or drug use disorder.
While we don't fully understand exactly why these two disorders are linked, it is possible that co-occurrence reflects overlapping environmental, genetic, or neurobiological factors. It is also possible that people use alcohol or drugs to self-medicate the depressive state, and/or that early drug use led to neurobiological changes that increase risk of depression. Heather Gotham, PhD, a Stanford clinical associate professor of psychiatry and behavioral sciences, notes:
It is very important to understand that if a person has both a mental health and a substance use disorder, then both disorders need to be treated at the same time. The thought used to be to treat one first, and then the other, but it is most effective to treat both at the same time, likely with a combination of medication and therapy or counseling. It is also very important that if a person is seeing multiple health care professionals for treatment, such as a psychiatrist for depression medication and an addiction counselor, that the professionals collaborate and are in contact about treatment.
Chronic physical disease
Depression also tends to be prevalent in people with chronic physical conditions. One explanation for why those with chronic disease are at higher risk for depression is that these chronic conditions can take away an individual's sense of independence and self-efficacy. These feelings can ultimately lead to depression.
It is also thought that inflammation, a byproduct of increased immune activity and a key part of diseases such as autoimmune disorders, diabetes, cardiovascular disease, cancer, and dementia, also affect depression as well. Inflammation can make the symptoms of depression worse, and studies have even shown that when inflammatory pathways are blocked, mood can be improved.
Realizing that poor health may be traced to the interplay between depression and another condition is a critical step toward feeling better. After all, depression interferes with diet, sleep, and the ability to take medications as prescribed, all of which can worsen other chronic diseases.
Depression can be masked by these other diseases. Symptoms like fatigue, lack of appetite, poor sleep, disinterest in daily life, and cognitive changes can be attributed to the chronic disease itself. As a result, increased awareness that depression can be linked to other conditions is paramount for more accurate diagnosis.
In this series, we have discussed a variety of different topics related to depression, a disease that affects more than 300 million people worldwide and is one of the leading causes of disability in adults. Through these posts, all of which have addressed a different topic related to the disease, we hope that our readers will better understand the condition itself, including diagnosis and symptoms, how and where to access adequate care, various treatments, different types of providers, and finally, conditions that are associated with depression.
By examining depression, we hope that we can empower people to not only seek care for themselves, but also seek care for those around them. We have far to go in ensuring that every person is receiving adequate care, but the first and most important step is to increase awareness and provide individuals with more knowledge of the disease.
This is the eighth and final post in a series, Taking Depression Seriously, that aims to help patients and family members better understand depression as a chronic disease and more successfully navigate the health care system.
Sophia Xiao is a masters degree student in Community Health and Prevention Research at Stanford University. She studies barriers to health care and the role of public health education in improving access to care. Stanford professor and primary care physician Randall Stafford, MD, PhD, studies strategies to improve chronic disease treatment, including increasing the role of patients in their health care.
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