Endogenous is a word that means “from within.” Psychiatrists and researchers once theorized that it was important to differentiate between endogenous (primarily biological and genetic in nature) and exogenous (reactive to stressful life events) types of depression.
They believed that treatments would necessarily vary depending upon that distinction.
However, early research into antidepressant medications failed to reveal the differences and the term “endogenous” largely has been absorbed into psychiatric literature to describe the melancholic features associated with major depressive disorder (MDD).
Studies from the 1980s and 90s found no statistical correlation between the effectiveness of antidepressants on depressions that were either biological in nature or caused by adverse life events. However, more recent research shows there are distinct differences between the two subtypes.
A report published in Molecular Psychiatry in 2012 found that “endogenous depression and chronic stress response are regulated by independent molecular pathways.” This led researchers to suspect that people who are more susceptible to stress may develop subtypes of depression that are distinct from endogenous ones. They suggest that it may be beneficial to develop new and novel treatments to help these patients. Research is ongoing.
Differences Between Endogenous and Exogenous Depression
For individuals with endogenous depression, symptoms often appear “out of nowhere” and for seemingly no reason. Endogenous depression is characterized by feelings of guilt and worthlessness and anhedonia. Anhedonia is the inability to derive pleasure from once pleasurable activities such as exercise, hobbies, or sex.
Although there is a significant amount of overlap between the two types of depression, the exogenous form is usually triggered by a highly stressful situation. It most often lacks physical symptoms such as changes in sleeping or eating habits. Although stressful events often precipitate both types of depression, people with the endogenous form are more likely to relapse than those whose depression is more reactive in nature.
One British study done in the 1990s found that, for those incurring a second depression, 70 percent with reactive depression had encountered severe stress shortly before their ?relapse. And only one third of those in the endogenous group had.
Symptoms of Endogenous Depression
As is the case with major depressive disorder, individuals with endogenous depression often experience anhedonia along with feelings of hopelessness, helplessness, worthlessness, guilt, or self-hate. Other symptoms that may accompany endogenous depression include:
- fatigue or lack of energy
- irritability and difficulty concentrating
- social isolation
- insomnia or hypersomnia (excessive sleeping)
- changes in appetite with corresponding weight gain or loss
- suicidal thoughts or behaviors
In more severe cases, patients may also experience psychotic symptoms such as hallucinations or delusions.
Diagnosis and Treatment
Because endogenous depression is a form of major depressive disorder, diagnosis and treatment is the same. A clinician or mental health professional will ask the patient a series of questions about their symptoms, medical history, and any substance abuse issues. Lab tests also are usually performed to rule out underlying physical causes such as a hormone imbalance.
The first line of treatment for endogenous forms of depression is usually medication—typically, a selective serotonin re-uptake inhibitor (SSRI)-type antidepressant. Additional treatments often consist of some form of talk therapy, such as cognitive behavioral therapy.
In more serious cases, antipsychotic drugs or electroconvulsive therapy (ECT) may be employed.
More on SSRIs
Contrary to what many people believe, SSRIs don’t increase serotonin levels in the brain.
Instead, they act by blocking serotonin re-uptake into the presynaptic cell. This allows additional serotonin to “slosh around” in the synaptic cleft, making it more available to bind to other receptors. Thomas A.M. Kramer, MD compares the misunderstandings regarding SSRIs to a boat sinking in the ocean. It’s like saying the boat “needs to have reduced water levels” without acknowledging that there’s water all around. Instead, he says, SSRIs “plug the holes” in the boat.
Research has shown, however, that SSRIs are generally no more effective than a placebo for mild to moderate forms of depression. But they are highly effective for more severe forms of depression, including MDD.
If you’re having thoughts of harming yourself or others, or if you’re a caregiver of such a person, call 9-1-1 or proceed to a hospital emergency room immediately.
You also may contact the National Suicide Prevention Lifeline 24 hours a day, seven days a week at 1-800-273-TALK (1-800-273-8255).