Many people at some point in their lives experience sadness and possibly even feel deeply depressed. However, when we talk about it in terms of the medical condition, major depressive disorder, it actually has stricter criteria that go beyond just the feelings of sadness. Major depressive disorder is a condition that affects aspects of emotion, cognition and behavior that result in a significant negative impact on a person's functioning and wellbeing. Diagnosing major depressive disorder is actually tricky since there is no simple laboratory test or questionnaire that can be used to make the diagnosis. In fact, major depressive disorder is what we call a diagnosis of exclusion, which means that in order to really diagnose someone with the disorder, you have to be able to rule out the other possibilities that could be underlying the symptoms. You have to make sure that it is not due to any other type of medical disorder or even if it is substance use or medication side effects. At present major depressive disorder remains a descriptive diagnosis that simply labels the conglomeration of core symptoms that affect emotion, cognition, and behavior, but it does not inform us at all about the processes or neurobiology related to the disorder.
History of the term
Depression is something that has been documented in human history for over a thousand years. There are reports of melancholia dating back to the time of ancient greeks. Its history has evolved over time, ranging from beliefs that it was caused by supernatural demonic possession to the time where it was seen as a personal weakness, evolving through the era of psychoanalysis to the modern era where we believe that it is an actual medical illness related to altered physiologic processes and brain function.
Symptoms of depression
Problems with emotional regulation is the symptom most people associate with depression. This is most commonly experienced as feelings of sadness, but there are also people that are not necessarily feeling sad, but experience anhedonia, which is the inability to experience pleasure or joy. The inability to experience joy or reward is believed to be associated at some level with another common symptom of amotivation, or the difficulty in initiating activities. Other people could also experience feelings of guilt, periods of irritability and problems with anger related to depression.
In addition, there are also core cognitive symptoms associated with the diagnosis. Individuals suffering form major depressive disorder commonly have problems with concentration. Many people report difficulties maintaining focus and the ability to sustain concentration on tasks. Others have difficulty shifting from one thought process to another. These people can get caught in ruminative thought patterns that are frequently associated with feelings of failure, worthlessness, and hopelessness. Many depressed individuals also report significant problems with indecisiveness, the inability to make even simple decisions. Most concerning, depressed individuals could also be caught in a cycle of morbid thoughts and become preoccupied by thoughts of death or even suicide. These are all symptoms believed to be reflecting some problems in regulating cognition.
The last group of symptoms is what we typically call the behavioral symptoms. Here we commonly talk about vegetative symptoms, such as changes in appetite, sleep and energy.
Classic melancholic depression is characterized by patients having a significant reduction in their appetite, problems falling and remaining asleep, and a slowing of physical actions. However, with other types of depression, including atypical depression, you may actually see opposite effects on appetite and arousal with overeating and increased time spent sleeping.