An estimated 16.1 million adults in the US struggle with depression, while an estimated 322 million people across the world have depressive symptoms. As a mental health disorder, depression comes in many different forms and with different levels of severity.
Severe depressive symptoms include self-harm and suicidal ideation, as well as suicide attempts. Mild symptoms of depression can still be debilitating, affecting one’s ability to work, maintain a healthy relationship with others, or function on a normal level. Some people struggle with depression tied to other conditions, including physical ones such as chronic or terminal pain.
Although it’s not completely understood why, people with depression often struggle with a second mental health disorder. Depression and anxiety are the most common combination, but other disorders include phobias, schizophrenia, and substance use disorder. Studies have observed that a large percentage (not the majority, but a sizeable minority) of patients struggling with one disorder also often show symptoms of another. It’s estimated that nearly a half of those who are diagnosed with depression also became diagnosed with an anxiety disorder.
Is it because the two are so similar? Is it a matter of one’s environment and upbringing? Could the answer lie deeper within the brain?
Why Depression Likes Company
In the 1970s, a renowned American epidemiologist discovered and demonstrated that people with one condition often also struggled with another condition, using rheumatic fever as an example. Dubbing the phenomenon, a ‘comorbidity’, the existence of comorbidities has since served to help the medical and psychiatric community understand more about individual disorders through the way they are linked with other disorders in patients who develop both.
Yet one of the greater challenges in identifying a comorbidity in patients with mental health issues is that one disorder can masquerade in part as another disorder. While depression and anxiety, for example, are very different disorders, it’s often the case that one condition is discovered and diagnosed before the other.
This is not an uncommon phenomenon. One sample taken in 2009 discovered that roughly half of patients with psychiatric conditions had more than one condition.
The reason why depression is linked with so many other conditions is in part because depression can cause other mental disorders, and in part because some mental disorders (and physical conditions) may be at the heart of why a person develops depressive symptoms. To understand how that might happen, it’s important to understand depression.
What is Depression?
Major depressive disorder is a collection of symptoms characterized by a chronically low mood. The hallmark of the disorder is sadness that lasts at least two weeks. Most cases of depression are temporary, yet severe. Some become chronic, with milder symptoms lasting years and decades. The causes of depression are complex and varied, from biological causes to environmental causes, and a combination of both.
Some people respond well to pharmacological treatment, which is the most common and readily available treatment for depression. When medication fails to elicit a proper response, other treatments might be used – including alternatives such as transcranial magnetic stimulation.
In cases where depression is part of a series of conditions, it may or may not play a role in the development of other mental health issues. Neurologically, some cases of depression are potentially caused by differences in neurotransmission, where some brains interpret or communicate differently. In other cases, depression is largely triggered by traumatic experiences. Some cases are different yet, with causes ranging from thyroid problems to brain tumors.
Depression and Anxiety
Major depressive disorder paired with generalized anxiety disorder is the most common combination, as both depression and anxiety are generally the most common mental health issues requiring treatment today. One affects the other in peculiar ways, yet both appear superficially similar.
Anxiety may lead to negative thoughts, low self-esteem, problems with self-perception, and a low mood. However, while depression is a low-energy disorder, anxiety is, in its own way, a high-energy disorder (as patients with anxiety disorders are prone to agitation and panic).
Pharmacological treatment is often effective, but therapy is critical. Both disorders are often treated through a combination of medication and cognitive-behavioral disorder.
Depression and Eating Disorders
Eating disorders are characterized by an unhealthy relationship to food, typically in the form of excessive eating, willful starvation, or a series of binges and purges. The two most common eating disorders are anorexia nervosa and bulimia nervosa.
While these conditions are much more common among women, men can struggle with eating disorders and body images as well. Depression ties into these disorders by feeding the negative thoughts that fuel them, often driving individuals to further feel negatively about themselves, and go through even harsher lengths to control their weight and eating habits.
Anorexia nervosa is characterized by self-imposed fasting, to an unhealthy degree. Individuals with anorexia often note that they feel their ability to eat or not to eat is the only real control they have over their lives, and many often struggle with a series of other symptoms suggesting an anxiety or depressive disorder.
Individuals with anorexia are diagnosed based on behavior and bodyweight – excessively low bodyweight, unhealthy eating patterns and forced fasting are all signs of anorexia.
Bulimia nervosa is characterized by binging and purging. It’s a cyclical condition wherein a person will give into a feeding frenzy, feeling temporarily elated, followed by deep shame and self-hatred, leading to self-induced vomiting.
Individuals with bulimia will rely on laxatives, exercise, and the gag reflex to purge. Side-effects of bulimia include damage to the throat and stomach due to frequent vomiting, as well as electrolyte imbalances, anemia, and other deficiencies. People with bulimia may be underweight, but often also have a normal bodyweight.
Other Mental Health Issues & Conditions
There are many more mental health issues that often pair with depression, including obsessive-compulsive disorder, addiction, and schizophrenia. However, there is no concrete evidence to suggest how or why depression is often combined with other mental health problems. Although many theories exist, they may not have a bearing on a patient’s treatment, as every case can be wildly different, responding only to a specific set of treatments.
Experimentation and trial-and-error is often a necessary part of the treatment process, as patients must undergo a series of first line treatments to find an approach that works and successfully reduces symptoms.