Biology 202
1998 Third Web Reports
On Serendip

Analysis of the Spectrum of Depression

Robert M. Miller

Depression has many degrees of severity from a passing feeling to a serious illness, which destroys lives and relationships. Major depressive disorder is the most severe form of depression. It is extreme and persistent, rendering the patient inconsolable and helpless (1). Depressed patients often cannot continue working and have difficulty dealing with family and friends. Other symptoms of major depression are deep despair, misery, irritability, low self-esteem, suicidal thoughts, change in eating and sleeping habits, fatigue and inability to concentrate. Other mental illnesses, such as anxiety and alcoholism are also associated with major depression (2). While serious depressive episodes are important to our understanding of mental health, chronic depression is terribly widespread and often undiagnosed or misdiagnosed. Dysthymia is a disorder which has similar, but milder and much longer lasting, symptoms to depression (3). By understanding the characteristics of dysthymia, health professionals can identify a chronic mental illness before it manifests into more serious psychological problems, such as severe depression. Dysthymia is also an interesting disorder from the neurobiological perspective because it is often difficult to discern from other personality disorders, such as a depressed or gloomy personality. This paper explores depression and dysthymia, their symptoms and therapies. In addition, personalities which are depressed will be analyzed and compared to depression and dysthymia. Do all three afflictions stem from the same genetic or environmental causes, and mechanistic origins? Are they all responsive to the same treatment? This comparison will address the difficulty in distinguishing mental illnesses and mood disorders from personality characteristics and traits.

Major depression is characterized by a hollow, empty feeling that is inescapable. The symptoms usually persist and are not easily alleviated. Good news or joyful events are not enough to snap someone out of depression. The most severe form of depression is known as a major depressive episode. Episodes such as these are one of the most common and treatable forms of mental illness. Often it is difficult to diagnose a patient with a major depressive episode, for the symptoms may be attributed to other ailments such as the flu or stress. The signs of depression are sometimes not recognized by family members and friends. Even if they are noticed, patients may refuse to be helped, stuck with the perception that all efforts are futile (2). Depression strikes more women than men. The lifetime risk of suffering from major depression is 10-25% for women and 5-12% for men. The average age of onset is 25 years old, but there is no correlation between depression and ethnicity, income or education (4). Depression reoccurs in approximately 80% of patients who have already experienced major episodes (4).

Diagnosing major depressive episodes can be a challenge if other mental or physical disorders are present. However a general criterion has been developed (4): An individual is clinically depressed if he or she meets the following four points:

A) Displays an abnormally depressed mood or exhibits an abnormal loss of all interest and pleasure, most of the day, almost everyday, for at least two weeks;

B) For the same two week period, five of the following symptoms are present and represent a change from the patient's normal behavior:
1. Significant weight loss when not dieting or weight gain (more than 5% of body weight in a month) or decrease in appetite. In children, failure to make expected weight gains.
2. Insomnia or hypersomnia.
3. Psychomotor agitation retardation which is noticeable to others, not merely subjective feelings of restlessness or being slowed down.
4. Fatigue or loss of energy.
5. Feelings of worthlessness, excessive or inappropriate guilt (which may be delusional).
6. Diminished ability to think or concentrate, or indecisiveness.
7. Recurrent thoughts of death (not just fear of dying, recurrent suicidal ideation without a specific plan, or suicide attempt or a specific plan for committing suicide.)

C) These symptoms must cause clinically significant distress or impairment in social, occupational or other important areas of functioning. D) The symptoms are not due to the direct physiological effects of a substance, general medical condition or normal bereavement.

Dysthymia is a slightly different disorder than depression. Those afflicted are usually able to continue working and conducting daily activities. Dysthymia often presents itself during childhood or adolescence. Symptoms such as poor school performance, social withdrawal, shyness, irritability, hostility and frequent conflicts with parents are the first indicators of the affliction (3). But the disorder can develop later in life as well. Symptomatic similarities exist between depression and dysthymia including early onset of REM sleep and other sleep disturbances. Dysthymia affects fewer individuals than major depression, approximately 3% of the population will suffer from dysthymia over the course of their lives (3).

While the distinction between a major depression episode and dysthymia is well defined, diagnosing dysthymia is often difficult. Mental health experts have outlined criteria for dysthymia similar to those developed for depression (5). The criteria are as follows:

A) The person must have a depressed mood for most of the day, for more days than not, for at least two years. In adolescents mood may be irritable.

B) The presence of two or more of the conditions in items B of the diagnoses for major depression.

C) During the two-year period, the person has not been without the above symptoms for more than two months at a time, nor has experienced a major depressive episode, manic episode, mixed episode or hypomanic episode.

D) Other mood disorders must also not be afflicting the person, such as cyclothymic disorder, schizophrenia or delusional disorder.

E) The symptoms are not due caused by direct physiological effects of a substance, a general medical condition or bereavement.

F) The symptoms must cause clinically significant distress or impairment in social, occupational or other important areas of functioning.

Differentiating dysthymia from a personality which is generally depressed or other personality disorders is particularly difficult. Prior to 1980, mental health professionals used the term "depressive personality" to encompass the symptoms of dysthymia, and this term still favored today by some psychiatrists (3). Many of the symptoms of dysthymia, such as shyness, brooding, poor self-image and antisocial behavior overlap with the diagnosable personality disorders avoidant, dependant, passive-aggressive, and obsessive compulsive (3). Unfortunately, there doesn't seem to be a specific definition of personality disorder compared to a mental illness. To further blur the distinction between dysthymia and a gloomy personality, patients often mask identifiable symptoms with other disorders, alcoholism, anxiety or eating disorders (6). The one clear distinction between the two forms of mild depression is that persons with a depressed character are aware and alert, able to continue functioning at work and at home, while dysthymics, by definition, are impaired by their disorder. Personality theory sheds very little light on this issue. A personality trait can be defined as a "susceptibility to certain states of mind and an inclination to certain behaviors (3)." Certain personality types have been studied and categorized, and may even be able to be measured. Personality tests such as the Myers-Briggs test can break down a person into one of sixteen different personality types through the use of an extensive questionnaire, but this taxonomy does not address or assist in defining a depressed personality (7). Stuart Dimond, a famous British neuropsychologist identified eight brain personality types based on the philosophy of phrenology, studying the bumps and fissures of the brain (8). Personality theory helps us to understand differences in people, however it does not necessarily differentiate between the two levels of mild depression.

The symptoms of all degrees of depression are similar, however they are not unique to depression. Diagnostic ambiguities between major depression and other mental illnesses, and between dysthymia and personality disorders are complicated issues. Major depression can often be addressed if a patient is able to unmask the true cause of other problems such as alcoholism and eating disorders. This is a difficult process. Separating dysthymia from personality traits is almost impossible due to the lack of clear definition between mood disorders, personality disorders and personality. "It is oversimplification to say that personality is enduring and mood is episodic, or even to say that personality is more fundamental and pervasive than mood." (3) It can be argued that persons with depressed personalities are more likely to succumb to more severe levels of depression. On the other hand, it could also be true that failures in mood regulation can exhibit emotional vulnerabilities and character traits that could be considered personality. In this sense it is difficult to make the argument for one common mechanism for depression.

There are many correlations between major depression, dysthymia and depressed personality which support the theory that the illnesses represent different stages, levels or presentations of an underlying mood regulation malfunction. It has been observed that up to 80% of patients suffering from dysthymia eventually develop major depression. Nearly half of all those diagnosed with major depression suffer from double depression; dysthymia coupled with a major depressive episode (3). Also most patients who are recovering from a major depressive episode experience mild, chronic depression which persists for years after the episode.

Major depression, dysthymia and personalities which are depressed occur more often in people who have a genetic predisposition for the illnesses. In a recent study of identical and fraternal twins, depression was found to correlated significantly more by heredity than by childhood environment. Depressive symptoms were most significantly linked among pairs of identical twins and correlated to a lesser extent between fraternal twins (9). It has also been shown that dysthymia is more common in the children of parents who suffer from major depression. Although childhood environment correlates less significantly than heredity, dysthymics and major depressed individuals reported more adverse parenting than a healthy control group (10). Many personality theories, including Hans Eysenck theory, state that personality and behavior is largely dependant on a person's genes (8). Using these theories, it can be deduced that generally depressed personalities are linked to genetics. There has also been research demonstrating the differences between dysthymia and major depression. It has been found that the cerebral blood flow ration is significantly lower for patients with major depression compared to double depression. Electroencephalogram (EEG) sleep patterns show differences between brain activity in patients suffering from depression and dysthymia. These EEG differences suggest that "dysthymia manifests primarily trait characteristics of depression, thus differentiating it from the state characteristics of major depression." (6) An additional study tested the effect of mood of patients by using ergopsychometric testing. Those with major depressive disorder displayed significantly better moods during testing, while those patients with dysthymia showed a deterioration in mood under the same conditions. These experiments support that major depression and dysthymia may not be as closely linked as we think, and the illnesses may not be different degrees of the same mechanistic failure in mood regulation (6). The neurobiological causes of major depression and dysthymia are under investigation, but no certain mechanism has been conclusively assigned for these illnesses. It is clear, however that neuroendocrine, neurochemical and autonomic abnormalities are involved in both afflictions (11). Research has shown that serotonin is a key neurotransmitter involved in mood disorders. It has been speculated that reduced levels of serotonin in the brain is responsible for depressed moods and other mental disorders. Serotonin is also involved in a myriad of other functions such as sleep and appetite regulation, self-control, aggression and anxiety (1). Fluctuations in serotonin would explain several symptoms of depression and dysthymia. Certain drugs that combat depression target serotonin and cause it to linger longer in the synapses between neurons (6).

Other theories about the causes of depression involve the hippocampi, which is thought to be involved in learning and memory. Intense or chronic stress can bring about large increases in the amount of the hormone cortisol which is released from the hippocampi. It has been speculated that this may cause the hippocampi to shrink, decreasing the ability to solve problems and remember. Cortisol is also responsible for increasing the magnitude of emotional responses from the amygdala. These emotional reactions are often exhibited as anxiety and fear, which explains why anxiety and depression are likely to coexist (1).

Observations of the pre-frontal cortex in depressed patients give additional clues into the mechanism of depression. In a study published in Nature, activity in this region of the brain, measured by positron emission topography of cerebral blood flow, was decreased in patients with major depression (11). Another study showed that the brain scans of depressed patients compared to healthy individuals showed tissue loss from the frontal lobe of the cerebral cortex.(6) This evidence leads to speculation that the emotional responses of patients with depression are affected by damage or incomplete development of the cerebral cortex. It is also been noted that cingulate gyrus, which regulates the release of neurotransmitters such as serotonin and norepinephrine, is abnormally small in these patients (1).

While most of the research regarding the neurochemical mechanism of depression does not specifically state that these imbalances take place in all forms of depression, we know that severe and mild groups can be treated effectively using the same medications, psychiatric treatments and psychotherapy. In considering the mechanisms which create depressed personalities, it is important to consider how people with such personalities respond to similar treatment. Antidepressants come in three classes, tricyclics, monoamine oxidase inhibitors (MAO's) and selective serotonin re-uptake inhibitors (SSRI's) There has been substantial evidence that all three classes work effectively for both dysthymia (1, 10) and major depression (1,6). All three types work on different aspects of the neuroanatomy. TCAs alter the brain's responses to norepinephrine and serotonin. MAO's act to block the function of the enzyme that breaks down norepinephrine and dopamine. SSRI's enhance the activity of serotonin by inhibiting its reabsorbtion into the nerve endings. All antidepressants work by adjusting the amounts of neurotransmitters working in the nervous systems, although certain drugs provide antidepressant action through unknown mechanisms (6). Other therapies such as electroconvulsive therapy (ECT) are safe and effective for treating the different degrees of depression. Almost half of all patients who do not respond to medication recover when given ECT (6). Psychotherapy is also an important strategy. Often medication is not effective without complimentary assistance in readjusting a patient's attitude toward life, stress and their own personality (6). Psychotherapy may be especially important in affecting patients with personalities which are considered depressed, without the need for medication.

Analyzing the evidence regarding the treatment of depression, is it not convincing enough to state that all levels of depression are related mechanistically. Antidepressant medication works with varying success for severe depression, however matching the patient with the right medication is often a matter of trial and error, signaling that depression is not the same in every individual (1). In the past, personality disorders or personality traits would have been named as the cause for many common symptoms, however today it is common for psychiatrists to diagnose mood disorders and dysthymia for the same symptoms (3). This phenomenon is due to the increasing success of antidepressant medication. Antidepressants have a positive effect on the symptoms of many mood and personality disorders, therefore proving their effective range is not limited to depression. Medication is often not effective for dysthymics and depressed personalities if there are more emotional issues at work than just depression (3). Psychotherapy coupled with drugs can often be a more reliable option. There is not enough evidence from treatment strategies that identifies one true mechanism for all forms of depression. In assessing whether the varying degrees of depression are in fact the result of one single mechanistic failure, the symptoms and treatment strategies are the most reliable evidence. Both of these approaches failed to conclusively prove this. Despite the significant genetic correlation among all forms of depression, there has not been found one definitive link that explains all levels of depression. Diagnosing and treating different degrees of depression is a significantly demanding task given the sheer number of other disorders that are at work in a given patient. The fact that so many neurochemical substances and mechanisms affect similar symptoms in many different disorders, indicates how complicated the biochemistry of mood disorders is. Behavioral and emotional signals can be influenced at several different levels in the brain, by a myriad of chemicals. The sole cause of depression seems to be the simultaneous breakdown of neurochemical pathways across the nervous systems. It is true that treating depression in all of its forms is much easier today with the advent of new antidepressants, but these drugs are correcting a neurochemical imbalance which is not specific to depression. There may exist and someday be discovered a particular mood regulation flaw which is responsible for depression, but given the research presented today, I would say there is not.


1) Elliott, Laura. "Help for Your Head, " Washingtonian, April 1998, p.76

2) APA Online-Depression- Background and ordering Information

3) Dysthymic Disorder- Dysthymia and Other Mood Disorders

4) Major Depressive Disorder- American Description

5) Dysthymic Disorder- American Description- Diagnostic Criteria

6) Articles on Mood Disorders- Update on Mood Disorders

7) Myers Briggs Personality Test

8) Importance Personality

9) Major Depressive Disorder- Heredity Vs. Environment in Depression

10) Dysthymic Disorder- Research Re: Cause

11) The Breaks of Emotion

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