Major Depression: An Overview

Major Depressive Disorder: DSM V Criteria

While you cannot diagnose mental health disorders, you should be familiar with their symptoms, as outlined in the DSM V.  According to the DSM V, a diagnosis of Major Depressive Disorder must meet the following criteria:

Specific symptoms, at least 5 of these 9, present nearly every day.

  1. Depressed mood or irritable most of the day
  2. Decreased interest or pleasure in most activities, most of each day
  3. Significant weight change (5 %) or change in appetite
  4. Change in sleep: Insomnia or hypersomnia.
  5. Change in activity: Psychomotor agitation or retardation.
  6. Fatigue or loss of energy
  7. Guilt/worthlessness: Feelings of worthlessness or excessive or inappropriate guilt
  8. Concentration: diminished ability to think or concentrate, or more indecisiveness
  9. Suicidality: Thoughts of death or suicide, or has suicide plan.

Source: Diagnostic and statistical manual of mental disorders: DSM-5. (2013). Arlington, VA: American Psychiatric Association.

Differential Diagnoses

Before proceeding with a depression protocol, you should rule out a few differential diagnoses.  Two common disorders that are often mistaken for depression are Seasonal Affective Disorder and Dysthymia.

According to the DSM V, a diagnosis of Seasonal Affective Disorder must meet the following criteria:

  1. The person must have had at least two episodes of depression in the past 2 years occurring at the same time of the year (most commonly, fall winter), and full remission must also have occurred at the same time of the year (most commonly, the spring).
  2. In addition, the person cannot have had other, nonseasonal depressive episodes in the same 2-year period, and many of the person’s lifetime depressive episodes must have been of the seasonal variety.

You should attempt to determine whether the symptoms are seasonal in nature (usually during the fall/winter) and whether the symptoms clear up during spring/summer. Prevalence rates suggest that winter seasonal affective disorder is more common for people living at higher latitudes (northern climates) and in younger people.

If you suspect that you may show symptoms of SAD, then a referral to a clinician who specializes in light box therapy may be necessary.  For more information on bright light therapy, please see the following article from the Harvard Health Blog:

Another common disorder that shows a lot of overlap with Major Depressive Disorder is Dysthymia.  Dysthymia is a mood disorder that can best be understood as a chronic (longer lasting) low-grade (lower intensity) form of depression.  Thus, clients with Dysthymia will have a longer history of a less intense form of depression (2 years or more).

Another common presenting issue that is often mistaken for depression is complicated grief.  Grief and depression have many overlapping symptoms, but the major difference is that grief does not lead to a loss of self-esteem while depression does.  Depression can eventually result from complicated grief, but it calls for a very different treatment protocol.

And finally, major depressive disorder should also be differentiated from postpartum dysphoria in which 50-70% of women report symptoms of depression shortly after giving birth.

Source: Diagnostic and statistical manual of mental disorders: DSM-5. (2013). Arlington, VA: American Psychiatric Association.


The Prevalence of a disorder refers to the proportion of cases in a given population and is a measure of how widespread a disorder is.  The incidence of a disorder refers to the rate of new cases each year and is a measure of the risk in developing/contracting a disorder.

The National Institute of Mental Health’s epidemiological survey in 2016 indicated the following:

  • Prevalence: 7% of the American Population had at least one episode of depression in that year.
  • Lifetime Prevalence: The Lifetime prevalence of mood disorders is estimated to be around 20%.
  • Gender: Major depressive episodes were higher in females (8.5%) compared to males (4.8%). Women are known to have higher rates of trait neuroticism which may account for these gender differences.  The roles many women fulfill also tend to give them less control and research confirms that women are more likely to ruminate which exacerbates depression.
  • Age: Major Depressive Disorder was highest among those ages 18-25 (10.9%).
  • Prognosis: The World Health Organization ranked depression the 4th leading cause of disability. By 2020, it will be the second leading cause.

Source: Major Depression. (n.d.). Retrieved March 20, 2018, from


There are multiple causal pathways to depression with many of the causes likely being sufficient but not necessary for onset to occur.

The Biological causes of depression

  • Genes: Twin studies show a moderate genetic influence. One promising candidate is the serotonin‐transporter gene—a gene involved in the transmission and reuptake of serotonin, which is one of the key neurotransmitters involved in depression. One can either have 2 short alleles, 2 long alleles or 1 of each to form three genotypes.  Some research suggests that those with 2 short alleles are at a genetic risk for developing depression when faced with stressful life situations.
  • HPA Axis Abnormalities: Some research suggests that Blood plasma levels are elevated in 20-40% of depressed patients and in 60-80% of severely depressed hospitalized patients. Trauma and intense stress in childhood can increase the reactivity of the HPA axis which becomes a vulnerability to depression later in life.
  • Hypothyroidism: Depression is correlated with low thyroid levels. If your client has been diagnosed with hypothyroidism work collaboratively with her doctor to set the course for treatment.
  • Neurological Differences: Depressed patients show lower left-side prefrontal cortex activity which is associated with approach behaviors and reward seeking.  The relatively higher right-side prefrontal cortex activity is associated with increased negative affect and hyper-vigilant behaviors.   Depressed patients also show increased amygdala activity.
  • Circadian Rhythms: Research with depressed patients also indicates that circadian rhythms become desynchronized and the size and magnitude of these rhythms is diminished. Depression may therefore sometimes be caused or exacerbated by circadian rhythm abnormalities.

The Psychological causes of Depression

  • Attributional Style: Attributional style refers to what you typically attribute the cause of a behavior or event to.  Attributional styles vary along three dimensions:  internal-external, global-specific and stable-unstable.  Depression is associated with an attributional style of internal, stable and global causes.  This means that depressed people tend to attribute negative events to individual causes (internal) that cannot be changed (stable) and that affect many different areas of life (global). This contrasts with explanatory styles that are external, specific and unstable.  This means that negative events are typically seen as being externally caused, changeable and being confined to certain domains of life.
  • Beck’s Cognitive Triad: Aaron T. Beck observed that depressed people tend to have 3 types of negative thoughts. These include negative thoughts about the self, other people and about the future.  Depressed peopled tend to see themselves as failures and as possessing unique flaws that make them unlovable. They also tend to have negative views about people in general and thus have little hope for the future.
  • Cognitive Distortions: Depression is maintained by systematic information processing biases. In level 1 we examined distortions in detail which are negative misrepresentations of reality.
  • Hopelessness Theory: Depression can also result when one perceives a lack of control over a negative outcome which makes the person feel hopeless. However, signs may begin to arise that control is possible, so depression shifts into anxiety as the person attempts to gain control.  The person then vacillates between beliefs that control is possible (anxiety) and that control is not possible (depression).   Anxiety surfaces when some hope returns. This is one possible explanation for the high degree of comorbidity that occurs between depression and anxiety.

The Social causes of Depression

  • Lack of Social Support and Social Skills: Depressed individuals have smaller and less supportive social networks, and many have a passive or passive-aggressive communication style which leads to unmet needs.  Depressed people therefore have less resources to utilize for dealing with life stressors and typically have fewer connections which leads to fewer opportunities. This creates a vicious cycle that maintains the disorder.
  • Interpersonal effects: Depressed people can become burdensome to others as those around them feel the need to provide sympathy, support and care on an ongoing basis. This can lead to resentment or simply fatigue and further strains the already weakened support network and fuels the cycle of isolation.

The Behavioral Causes of Depression

  • Learned Helplessness: Seligman did a series of experiments in which he exposed dogs to uncontrollable shocks and then put them in aversive situations where escape was possible. However, after being exposed to the shocks the dogs lost the drive to even attempt escape.  It was as if they had learned a sense of helplessness that had generalized and prevented future attempts at control even when control was available.  The dogs serve as an analogy for those people who experience uncontrollable stressors (often in youth) and learn a sense of helplessness that generalizes to become the dominant mode of being.  This general sense of helplessness is similar to the symptoms and beliefs that many depressed people experience.
  • Lack of Rewards: From a behavioral perspective, depression is also sometimes caused by an unresponsive environment or a lack of experiences that cause feelings of pleasure and accomplishment.  The passive and hopeless beliefs that depressed people adopt cause them to withdraw and cease to have rewarding experiences.

Source: Hooley, J. M., Butcher, J. N., Nock, M., & Mineka, S. (2017). Abnormal psychology. Boston: Pearson.

The Brain and Depression
In a landmark study done in 1999 by the Archives of Internal Medicine concluded that exercise was just as effective in treating depression as medication is. 156 participants were divided into three
groups: the medication group, the exercise group and a group that exercised and received medication. After 16 weeks there were no significant differences between the groups as around 65% of people were no longer depressed. While the medication group became less depressed faster, after a certain amount of time exercise yields the same results.

Researchers did a follow up study with 133 of the original participants six months after the study and found that those who continued exercising had much lower rates of depression compared to everyone else.  This means exercise seems to work slower but has longer-lasting effects compared to medication.  Exercise seems to increase endorphin release which numbs the pain that depressed people feel. Exercise releases endogenous morphine as opposed to drugs that mimic the effects of endorphins.

Depression is also associated with a malfunctioning arousal-regulation system. When you are depressed your arousal system is tuned too low. In a highly stimulating environment the brain down-regulates its responsiveness too much and in a low-stimulation environment your brain doesn’t up-regulate enough. Neurotransmitters like Serotonin are thought to be involved in these processes and depressed people show deficiencies here.  Brain scans reveal that those who suffer from major depression have substantially fewer serotonin receptors in their midbrain than do non-depressed people.  The midbrain contains the hypothalamus and the limbic system and is associated with mood regulation. Depression is associated with reduced sensitivity to serotonin in these regions of the brain.

One emerging theory suggests that the key to overcoming depression is to stimulate neurogenesis or making new neurons in the brain. Research confirms that people who suffer from depression for several months have smaller hippocampus regions.

People who suffer from inflammation-related diseases are also more likely to suffer from depression. There may be a link between inflammation and depression but right now the relationship is correlational.   Some research suggests that eating fermented foods can help you with depression. Fermentation involves exposing foods to a type of bacteria called lactobacilli. These bacteria convert the sugars in foods into lactic acid which tastes sour. Some examples of fermented foods include: kimchi, sauerkraut, yogurt, sourdough bread, tempeh and miso.  Some research suggests that the incidence of depression is lower in people who eat fermented foods but right now this is correlational and we aren’t sure why.

Source: Outsmart Yourself

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