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Depression; Diagnosis, Types, Causes and Treatments

Updated: Apr 1, 2021

20% of the global population experiences at least one depressive episode before turning 18. Women are two times more likely to have clinical depression. Over 50% of depressed people do not get the help they need. The risk of suicide rises to 20 times in depressed individuals as opposed to non depressed ones.

Signs And Symptoms Of Depression?

Depression symptoms can vary from mild to severe and can include:

  • Persistent sad, anxious, or “empty” mood

  • Feelings of hopelessness or pessimism

  • Feelings of guilt, worthlessness, or helplessness

  • Difficulty thinking, concentrating or making decisions

  • Loss of interest or pleasure in activities once enjoyed, also called anhedonia

  • Restlessness or irritability

  • Changes in appetite — weight loss or gain unrelated to dieting

  • Trouble sleeping or sleeping too much

  • Loss of energy or increased fatigue

  • Aches or pains, headaches, cramps, or digestive problems without a clear physical cause and/or that do not ease even with treatment

  • Thoughts of death or suicide or suicide attempts

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For a diagnosis of clinical depression, most or all these symptoms must be present for at least 2 weeks, and affect your socio-occupational functioning. Mental health professionals often ask people to complete questionnaires to help assess the severity of their depression. The Hamilton Depression Rating Scale, for example, has 21 questions. The scores indicate the severity of depression among people who already have a diagnosis. The Beck Depression Inventory is another questionnaire that helps mental health professionals measure a person’s symptoms.

How Depression Symptoms Vary With Gender And Age

Depression In Men

Depressed men are less likely to acknowledge feelings of self-loathing and hopelessness. Instead, they tend to complain about fatigue, irritability, sleep problems, and loss of interest in work and hobbies. They’re also more likely to experience symptoms such as anger, aggression, reckless behaviour, and substance abuse.

Depression In Women

Women are more likely to experience depression symptoms such as pronounced feelings of guilt, excessive sleeping, overeating, and weight gain. Depression in women is also impacted by hormonal factors during menstruation, pregnancy, and menopause. In fact, postpartum depression affects up to 1 in 7 women.

Depression In Teens

Irritability, anger, and agitation are often the most noticeable symptoms in depressed teens—not sadness. They may also complain of headaches, stomach aches, or other physical pains.

Depression In Older Adults

Older adults tend to complain more about the physical rather than the emotional signs and symptoms of depression: things like fatigue, unexplained aches and pains, and memory problems. They may also neglect their personal appearance and stop taking critical medications for their health.

Depression Is Different From Sadness or Grief/Bereavement

The death of a loved one, loss of a job or the ending of a relationship are difficult experiences for a person to endure. It is normal for feelings of sadness or grief to develop in response to such situations. Those experiencing loss often might describe themselves as being “depressed”. But being sad is not the same as having depression. Grief and depression are different in important ways:

  • In grief, painful feelings come in waves, often intermixed with positive memories of the deceased. In major depression, mood and/or interest (pleasure) are decreased most of the time.

  • In grief, self-esteem is usually maintained. In major depression, feelings of worthlessness and self-loathing are common.

  • In grief, thoughts of death may surface when thinking of or fantasizing about “joining” the deceased loved one. In major depression, thoughts are focused on ending one’s life due to feeling worthless or undeserving of living or being unable to cope with the pain of depression.

Grief and depression can co-exist. For some people, the death of a loved one, losing a job or being a victim of a physical assault or a major disaster can lead to depression. When grief and depression co-occur, the grief is more severe and lasts longer than grief without depression.

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What Are The Different Types Of Depression?

The most common forms of depression are:

  • Major Depression: having symptoms of depression most of the day, nearly every day for at least 2 weeks that interfere with your ability to work, sleep, study, eat, and enjoy life. An episode can occur only once in a person’s lifetime, but more often, a person has several episodes.

  • Recurrent, Mild Depression (Dysthymia): Dysthymia is a type of chronic “low-grade” depression. More days than not, you feel mildly or moderately depressed, although you may have brief periods of normal mood. The symptoms of dysthymia are not as strong as the symptoms of major depression, but they last a long time (at least two years). Some people also experience major depressive episodes on top of dysthymia, a condition known as “double depression.” If you suffer from dysthymia, you may feel like you’ve always been depressed. Or you may think that your continuous low mood is “just the way you are.”

  • Perinatal Depression: Women with perinatal depression experience full-blown major depression during pregnancy or after delivery (postpartum depression).

  • Seasonal Affective Disorder (SAD): SAD is a type of depression that comes and goes with the seasons, typically starting in the late fall and early winter and going away during the spring and summer.

  • Psychotic Depression: This type of depression occurs when a person has severe depression plus some form of psychosis, such as having disturbing false fixed beliefs (delusions) or hearing or seeing upsetting things that others cannot hear or see (hallucinations).

  • Atypical Depression: Many people with depression don't have the typical symptoms, with symptoms that include weight gain, sleeping too much, and feeling anxious.

  • Bipolar Depression (Manic Depression): Here, depression is part of Bipolar Disorder, which means that it alternates with episodes of elation or mania.

What Is The Course Of Depression?

Depression is a recurring disorder, and about 50% of people who have one episode of depression have another. Studies show that the number of life stressors a person experiences influences the likelihood of recurrence. They also show that likelihood of recovery declines the longer that episodes last. There is some

evidence that depression itself changes the brain, diminishing the ability to form new nerve cell connections and decreasing brain reserves, thereby curtailing the capacity for recovery.

How Long Do Episodes Last?

Researchers have found that the median duration of a first episode of depression is 17 weeks, or about four months. There is a very high probability of recovery in the early weeks of a depressive episode. The severity of a first episode of depression, essentially the degree to which the body is functionally impaired, or in shutdown mode, seems to exert some influence on the likelihood of a recurrent episode.

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Does Depression Ever Go Away On Its Own?

Depressive episodes may lift on their own, but even in the best-case scenario that can take many months and in the interim do significant damage to both your brain and your life. Experts believe that the inflammation involved in depression can, over time, contribute to neurodegeneration and, in a vicious cycle, accelerate pathologic changes in the brain that make future recovery more elusive.

Is Depression Curable?

While there is no cure for depression, there are effective treatments that help with recovery. The earlier treatment starts, the more successful it may be. Many people with depression recover after following a treatment plan. However, even with effective treatment, however, a relapse may occur. To prevent relapse, you should continue with treatment, even after symptoms improve or go away, for as long as your doctor advises.

Depression Causes And Risk Factors

There is no single known cause of depression. Rather, it likely results from a combination of genetic, biological, environmental, and psychological factors. Let’s look at them one by one:

Genetics: Depression can run in families. For example, if one identical twin has depression, the other has a 70% chance of having the illness sometime in life. A person with a parent or sibling who has depression is two-to-three times more likely than the general public to develop the condition. However, many people with depression have no family history of it.

Biological: Certain medications, such as barbiturates, corticosteroids, benzodiazepines, opioid pain killers, and specific blood pressure medicines can trigger depression symptoms in some people, as can hypothyroidism (an under-active thyroid gland). Medical conditions, such as obesity, heart disease, and diabetes also contribute to depression. Biological factors may or may not be associated with medical conditions or induced by medications, and certainly play a role in depression. Let’s look at them one by one:

  1. Inflammation: There is growing evidence that depression gives rise to inflammation and the inflammatory response creates or exacerbates depression. Negative thoughts are a source of psychological pain. Like all signs of injury, even psychological pain mobilizes various immune cells to help subdue the source, and that mobilization creates inflammation. Stress is known to activate an inflammatory response. The presence of inflammatory cells in the brain may be one reason many drug treatments for depression fail; they do not target inflammation. Cortisol levels are consistently high in depressed people, and that’s a fair indicator of stress.

  2. Hormonal changes: Under normal conditions, serotonin inhibits pain, influences the processing of various emotions, and mediates many mental capacities important in social life. But its production and activity are affected by the hormones the body secretes in response to threat or stress, such as cortisol. One result is a functional lack of serotonin, which, among other things, disrupts the circuitry that regulates moral emotions. Growing evidence suggests that is why those who are depressed are haunted by excessive self-blame and a sense of guilt. The neurotransmitter dopamine, which mediates motivation and desire, is one of several brain signaling chemicals that are implicated in depression. It is associated with two of the most prominent features of depression—anhedonia, or the inability to experience pleasure, and appetite alterations. Many neurons that use dopamine to relay signals are sensitive to the effects of stress, which can alter their excitability and activity. Studies have also shown that reward-generating areas of the brain—such as the nucleus accumbens, where dopamine signals originate—may be underactive in depression.

  3. Faulty Circuitry: Neurotransmitters are only one part of a much larger story of how nerve cells function in circuits to relay messages from one part of the brain to another. In fact, many experts see depression as a nerve circuit disorder, marked by a power failure in the brain’s wiring, affecting communication between one area of the brain and another. The nerve cell connections between the amygdala and the prefrontal cortex (PFC) are sometimes called the “depression circuit"; depression results when emotion-laden signals from the amygdala overpower the ability of the PFC to regulate the signals. The prolonged or excessive release of stress hormones can lead to a failure of activation of key nodes in neural networks or impair the strength of signals between them, especially when processing emotion-related or reward stimuli.

  4. Brain Shrinkage: One consequence of uncontrolled stress is shrinkage of the hippocampus, manifest in the impaired memory and learning that are characteristic of depression. Cortisol also turns off the generation of new nerve cells in some areas of the brain, affecting the circuitry of the brain. In addition, prolonged cortisol exposure affects production of the insulating myelin sheath surrounding nerve cells, diminishing the overall efficiency or nerve signalling.

  5. Abnormal activity in certain parts of the brain, mainly hypoactivity of the dorsolateral prefrontal cortex, has been observed in depression. This lower than normal functioning of the prefrontal cortex results is little to no control over the emotional centre, the amygdala, causing worsening of mood in a vicious cycle. This area of the brain is the target of most noninvasive brain stimulation procedures.

  6. Disruption of the sleep-wake cycle is one of the hallmarks of depression and is a major source the mood disturbance in major depression. Lack of sleep upsets the body’s circadian clock that orchestrates the natural daily rhythm of most biological functions, including patterns of secretion, release, and activity of many neurochemicals in the brain. Sleep deprivation is thought to impede the transmission of neural signals. Sleep deprivation impairs the brain’s ability to control negative thoughts. This is why depressed people are so irritable all the time.

Environmental Factors

  1. Loneliness And Isolation: There’s a strong relationship between loneliness and depression. Not only can a lack of social support heighten your risk for depression, but having depression can cause you to withdraw from others, exacerbating feelings of isolation.

  2. Marital Or Relationship Problems: While a network of strong and supportive relationships can be crucial to good mental health, troubled, unhappy, or abusive relationships can have the opposite effect and increase your risk for depression.

  3. Recent Stressful Life Experiences: Major life changes, such as a bereavement, divorce, unemployment, or financial problems can often bring overwhelming levels of stress and increase your risk of developing depression.

  4. Chronic Illness or Pain: Unmanaged pain or being diagnosed with a serious illness, such as cancer, heart disease, or diabetes, can trigger feelings of hopelessness and even lead to depression.

  5. Early Childhood Trauma or Abuse: Early life stresses such as childhood trauma, abuse, or bullying can make you more susceptible to a number of future health conditions, including depression.

  6. Alcohol or Drug Abuse: Substance abuse can often co-occur with depression. Many people use alcohol or drugs as a means of self-medicating their moods or cope with stress or difficult emotions. If you are already at risk for depression, abusing alcohol or drugs may push you over the edge. There is also evidence that those who abuse opioid painkillers are at greater risk for depression.

Psychological Factors

Personality: Whether your personality traits are inherited from your parents or the result of life experiences, they can impact your risk of depression. For example, you may be at a greater risk if you tend to worry excessively, have a negative outlook on life, are highly self-critical, or suffer from low self-esteem. These traits are called neurotic traits.

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How Is Depression Treated?

The first step in getting the right treatment is to visit a mental health professional, such as a psychiatrist. Your psychiatrist do an interview, and advise lab tests to rule out other health conditions that may have the same symptoms as depression. In some cases, reversing the medical cause would alleviate the depression-like symptoms. The evaluation will identify specific symptoms and explore medical and family histories as well as cultural and environmental factors with the goal of arriving at a diagnosis and planning a course of action. Once diagnosed, depression can be treated with lifestyle changes, supplements, medications, psychotherapy, brain stimulation therapies, or a combination of these. As a general rule, combination works better than single treatment. Let’s look at them one by one.

Lifestyle Changes

Food And Diet

Numerous studies link traditional Mediterranean-type and Japanese-style diets with low risk of depression. Both eating patterns involve lots of fruits, nuts and vegetables, fish more than meat, oils rather than solid fats, and moderate to minimal dairy consumption.

Exercise And Sunlight

Studies show that moderate-intensity aerobic exercise, such as brisk walking for 20 to 40 minutes three times per week for six weeks, significantly alleviates many symptoms of depression, and is especially effective at relieving physical symptoms, including sleep disturbance. What’s more, the benefits of exercise are long-lasting. This is because exercise raises core body temperature, which in turn creates feelings of relaxation and tension-relief. Exercise also promotes the release of endorphins, neurochemicals that have a direct mood-boosting effect. But the most enduring effect of exercise may be that it stimulates the release of nerve growth factors in the brain, leading to the growth of new nerve cells and new connections, literally opening new channels for thinking and acting. Also, sustained lack of sun exposure dysregulates production of hormones such as melatonin and serotonin that affects nerve function and cognitive processes. Sunlight exposure resets the body clock, begets healthy blood flow in the brain, and triggers body production of vitamin D. Studies show that vitamin D plays important roles in maintaining brain health, stimulating the growth of nerve cells to preserve memory and executive function and sustaining mood.

Nutritional Supplements

1. The B Vitamins, and especially folate (B9), pyridoxine (B6), and cobalamin (B12)—are crucial for nervous system function and play multiple roles in maintaining brain health. All the B vitamins are cofactors for enzymes involved in production of neurotransmitters that influence mood.

2. The mineral Magnesium also reduces inflammatory substances in the body; additionally it stabilises the levels of some neurotransmitters linked to depression.

3. Omega-3 Polyunsaturated Fatty Acids counter inflammation and are neuroprotective, reversing the nerve cell degeneration that is an effect of depression.

4. S-Adenosyl Methionine (SAMe): This is a synthetic form of a natural chemical in the body. This may help boost production of serotonin, the neurotransmitter in the brain that affects a person’s mood.


In the brain, electrical signals send messages from nerve cell to nerve cell but are relayed by chemical signals across the tiny gap between nerve cells. Antidepressant drugs affect those neurotransmitters, such as norepinephrine, serotonin, dopamine and others belonging to a class of chemicals known as monoamines.

Antidepressants may produce some improvement within the first week or two of use yet full benefits may not be seen for two to three months. Researchers believe that the time lag for response to medications is due to the development of new nerve cell connections; neuroplasticity. These medications are not sedatives. They are not habit-forming. Generally antidepressant medications have no stimulating effect on people not experiencing depression.

Antidepressants can have side effects, but many side effects may lessen over time. Talk to your psychiatrist about any side effects that you have. Do not stop taking your antidepressant without first talking to your psychiatrist. Psychiatrists usually recommend that patients continue to take medication for six or more months after the symptoms have improved. Longer-term maintenance treatment may be suggested to decrease the risk of future episodes for certain people at high risk.


Psychotherapy, or “talk therapy”, helps by teaching new ways of thinking and behaving, and changing habits that may be contributing to depression. Therapy can help you understand and work through difficult relationships or situations that may be causing your depression or making it worse. Psychotherapy also helps people develop effective coping strategies, important not only in relieving a current episode of depression but in preventing future ones.

Psychotherapy is sometimes used alone for treatment of mild depression; for moderate to severe depression, psychotherapy is often used along with antidepressant medications. Studies show that the benefits of Psychotherapy can be seen after 12 to 16 weekly sessions in a therapist’s office.

Brain Stimulation Therapies

  1. Cranial Electrotherapy Stimulation is a simple treatment employing a small, battery-powered device. The CES device sends pulses of very low amperage (i.e., less than 1.0 milliampere) electricity through thin wires attached to electrodes clipped to the ear lobes. The frequency of the electrical pulses is 100 Hz. CES causes release of endorphins, serotonin and norepinephrine.

  2. Audio-Visual Entrainment works by using rhythmic sound and flashing lights, to alter the frequency of brainwaves. Since different frequencies of brainwaves are emitted during different states of mind, altering the frequency of the brainwaves to that of relaxation, can be used for therapeutic benefit in depression.

  3. Low Intensity Transcranial Pulsed Electromagnetic Field Therapy works on low intensity electromagnetic field induction (10 milli Tesla). At this intensity, it works at the cellular level, by enhancing cellular voltage and nutrient intake, which balances hormonal functions including Serotonin (which helps us feel calm, serene, optimistic, and self confident) and Dopamine (responsible for making us feel excited, motivated, and energised).

  4. Transcranial Direct Current Stimulation (tDCS) applies a weak electrical current to brain sites through the scalp from a headset-like device. The goal is to target brain circuits involved in attention, perception, learning, and memory that affect mood.

  5. Electroconvulsive Therapy (ECT) is a medical treatment that has been most commonly reserved for patients with severe major depression who have not responded to other treatments. It involves a brief electrical stimulation of the brain while the patient is under anaesthesia, causing a clinical seizure.

  6. Ketamine, long used as an anaesthetic, is now also used in depression. Infused intravenously in carefully titrated doses over a period of 1 hour, it is very fast-acting, relieving symptoms within hours, with the effects of a single infusion lasting for days or a few weeks, in about 50 percent of patients. It is especially useful for helping patients troubled by suicidal ideation and is widely used in emergency psychiatry. Ketamine increases the levels of BDNF, and this forms new connections between nerve cells, and in a way, “resets” the brain to think more positively.

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