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Focus on depression

Depression is one of today’s most common illnesses. Our focus article explores the causes, the complexities surrounding diagnosis, and the treatments available.

Article by Fiona North
Focus on depression

Definition: "A mental condition characterised by feelings of severe despondency and dejection, typically also with feelings of inadequacy and guilt, often accompanied by lack of energy and disturbance of appetite and sleep."

Today, people often use the word ‘depression’ interchangeably with ‘sadness’. However, we cannot stress enough that sadness and depression are NOT the same thing. The former is a natural emotion, a temporary reaction to a particular situation or life change. It can manifest in feelings of loneliness, sorrow and helplessness, but fortunately, sadness fades away over time. Depression isn't an emotion it's a malfunction in the brain, as physical a reality as any other disease. Once you understand this fundamental difference between the two words, you’ll begin to realise that depression cannot be lifted at will, or wished away; you cannot talk someone out of depression any more than you can talk someone out of diabetes or heart disease. 

Depression is also an incredibly complex illness, and therefore unique to each individual. It isn’t simply the result of having too much or too little of a certain brain chemical; many chemicals are involved, working both inside and outside nerve cells. In fact there are millions, even billions, of chemical reactions that make up the dynamic system that is responsible for our mood, perceptions, and how we experience life. Together with other possible causes of depression, including faulty mood regulation by the brain, genetic vulnerability, stressful life events, medications, and medical problems, you can see how two people might have similar symptoms of depression, but the problem on the inside, and therefore what treatments will work best, may be entirely different.  

AREAS OF THE BRAIN ASSOCIATED WITH DEPRESSION

Amygdala: The amygdala is associated with emotions such as anger, pleasure, sorrow, fear, and sexual arousal. It is activated when you recall emotionally charged memories. Activity in the amygdala is higher when a person is sad or clinically depressed. 

Thalamus: The thalamus receives most sensory information and relays it to the appropriate part of the cerebral cortex, which directs high-level functions such as speech, behavioural reactions, movement, thinking and learning. Some research suggests that bipolar disorder may result from problems in the thalamus, which helps link sensory input to pleasant and unpleasant feelings.

Hippocampus: The hippocampus has a central role in processing long-term memory and recollection. Interplay between the hippocampus and the amygdala might account for the adage "once bitten, twice shy." It is this part of the brain that registers fear when you are confronted by an aggressive dog, and the memory of such an experience may make you wary of dogs you come across later in life. The hippocampus is smaller in some depressed people, and research suggests that ongoing exposure to stress hormones impairs the growth of nerve cells in this part of the brain.nerve cell communication.

Neurotransmitters are chemicals in the brain that relay messages from brain cell to brain cell (neuron to neuron). The following are a few believed to play a role in depression:
a) Acetylcholine enhances memory and is involved in learning and recall.
b) Serotonin helps regulate sleep, appetite, and mood and inhibits pain. Research supports the idea that some depressed people have reduced serotonin transmission. Low levels of a serotonin byproduct have been linked to a higher risk for suicide.
c) Norepinephrine constricts blood vessels, raising blood pressure. It may trigger anxiety and be involved in some types of depression. It also seems to help determine motivation and reward.
d) Dopamine is essential to movement. It also influences motivation and plays a role in how a person perceives reality. Problems in dopamine transmission have been associated with psychosis, a severe form of distorted thinking characterised by hallucinations or delusions. It's also involved in the brain's reward system, so it is thought to play a role in substance abuse.
e) Glutamate is a small molecule believed to act as an excitatory neurotransmitter and to play a role in bipolar disorder and schizophrenia. 
f) Lithium carbonate, a well-known mood stabiliser used to treat bipolar disorder, helps prevent damage to neurons in the brains of rats exposed to high levels of glutamate. Other animal research suggests that lithium might stabilise glutamate reuptake, a mechanism that may explain how the drug smooths out the highs of mania and the lows of depression in the long term.
g) Gamma-aminobutyric acid is an amino acid that is believed to act as an inhibitory neuro-transmitter. It is thought to help quell anxiety.

SIX COMMON TYPES OF DEPRESSION

Major depression. The classic depression type, major depression is a state where a dark mood is all-consuming and one loses interest in activities, even ones that are usually pleasurable. Symptoms of this type of depression include trouble sleeping, changes in appetite or weight, loss of energy, and feeling worthless. Thoughts of death or suicide may occur. It is usually treated with psychotherapy and medication. For some people with severe depression that isn't alleviated with psychotherapy or antidepressant medications, electroconvulsive therapy may be effective.

Persistent depressive disorder. Formerly called "dysthymia," this type of depression refers to low mood that has lasted for at least two years but may not reach the intensity of major depression. Many people with this type of depression type are able to function day to day, but feel low or joyless much of the time. Other depressive symptoms may include appetite and sleep changes, low energy, low self-esteem, or hopelessness.

Bipolar disorder. People with bipolar disorder – once known as manic-depressive disease – have episodes of depression, but they also go through periods of unusually high energy or activity. Manic symptoms look like the opposite of symptoms of symptoms: grandiose ideas; unrealistically high self-esteem; decreased need for sleep; thoughts and activity at higher speed; and ramped-up pursuit of pleasure including sex sprees, overspending, and risk taking. Being manic can feel great, but it doesn't last long, can lead to self-destructive behaviour, and is usually followed by a period of depression. Medications for bipolar disorder are different from those given for other depression types, but can be very effective at stabilising a person's mood.

Seasonal affective disorder (SAD). This type of depression emerges as days get shorter in the Autumn and Winter. The mood change may result from alterations in the body's natural daily rhythms, in the eyes' sensitivity to light, or in how chemical messengers like serotonin and melatonin function. The leading treatment is light therapy, which involves daily sessions sitting close to an especially intense light source. The usual treatments for depression, such as psychotherapy and medication, may also be effective.

Depression types that are unique to women

Postnatal depression. This type of depression includes major and minor depressive episodes that occur during pregnancy or in the first 12 months after delivery (also known as postpartum depression). Postnatal depression affects up to one in seven women who give birth and can have devastating effects on the women, their infants, and their families. Treatment includes counselling and medication.

PMDD. This type of depression is a severe form of premenstrual syndrome, or PMS. Symptoms of PMDD usually begin shortly after ovulation and end once menstruation starts. Selective serotonin reuptake inhibitors (SSRIs), may reduce symptoms.

CAUSES OF DEPRESSION

Stressful life events

At some point, nearly everyone encounters stressful life events. Some must cope with the early loss of a parent, violence, or sexual abuse. While not everyone who faces these stresses develops a mood disorder – in fact, most do not – stress plays an important role in depression. When a physical or emotional threat looms, the hypothalamus secretes corticotropin-releasing hor- mone (CRH), which has the job of rousing your body. CRH follows a pathway to your pituitary gland, where it stimulates the secretion of adrenocorticotropic hormone (ACTH), which pulses into your bloodstream. When ACTH reaches your adrenal glands, it prompts the release of cortisol. The boost in cortisol readies your body to fight or flee. Your heart beats faster – up to five times as quickly as normal – and your blood pressure rises. Your breath quickens as your body takes in extra oxygen. Sharpened senses, such as sight and hearing, make you more alert. Normally, a feedback loop allows the body to turn off “fight-or-flight” defenses when the threat passes. In some cases, though, the floodgates never close properly, and cortisol levels rise too often or simply stay high. This can contribute to problems such as high blood pressure, immune suppression, asthma, and depression.

Early losses and trauma

Certain events can have lasting physical, as well as emotional, consequences. Profound early losses, such as the death of a parent or the withdrawal of a loved one’s affection, may resonate throughout life, eventually expressing themselves as depression. When an individual is unaware of the wellspring of his or her illness, he or she can’t easily move past the depression.

Genes

Depression is known to run in families, suggesting that genetic factors contribute to the risk of developing this disease. However, research into the genetics of depression is in its early stages, and very little is known for certain about the genetic basis of depression. Studies suggest that variations in many genes, each with a small effect, may combine to increase the risk of developing depression.

Medical problems

Certain medical problems are linked to lasting, significant mood disturbances. Among the best-known culprits are two thyroid hormone imbalances. An excess of thyroid hormone (hyperthyroidism) can trigger manic symptoms. On the other hand, hypothyroidism, a condition in which your body produces too little thyroid hormone, often leads to exhaustion and depression. 

Mood stabilisers

Mood stabilisers reduce the severity and frequency of mood swings. These drugs are important for treating people with bipolar disorder. Common mood stabilisers include:

  • lithium carbonate
  • sodium valproate
  • carbamazepine

Tranquillisers

These medications are divided into 'minor' or 'major' tranquillisers. Minor tranquillisers (typically benzodiazepines) are not helpful in depression; they are addictive and can make the depression worse. Major tranquillisers are very useful for people experiencing psychotic depression or depression that isn't improving with other medications.

THERAPIES

Mindfulness meditation

In our busy world, multitasking is a way of life. But in the rush to accomplish necessary tasks, we often lose our connection with the present moment. We sprint through daily activities without being truly attentive of what we’re doing and how we’re feeling. Mindfulness is an antidote to this. It is the practice of focusing attention on what is happening in the present – and accepting it without judgment. Some experts believe that it works, in part, by calming the body’s stress response about the future, or regrets over the past.

Exercise

Many studies have found that regular exercise can improve mood in people with mild to moderate depression. One theory is based on the fact that exercise enhances the action of endorphins in the body. These chemicals can increase natural immunity, reduce the perception of pain, and possibly improve mood. Another hypothesis is that exercise stimulates the neurotransmitter norepinephrine, which may directly improve mood. But as scientists have learned more about how exercise affects nerve cells, another theory has gained ground – that the power of exercise, like antidepressants, lies in its ability to generate new nerve cells

Vagus nerve stimulation

Extending from the brain through the chest to the abdomen, the vagus nerve helps control your breathing and is linked to the amygdala, hypothalamus, and other parts of the brain that regulate mood and anxiety. A vagus nerve stimulator is a surgically implanted device similar to a pacemaker that delivers a small electrical impulse to this nerve for about 30 seconds every five minutes. 

rTMS

rTMS is a mild form of brain stimulation, and used to treat depression when patients have not responded to antidepressant medication. Magnetic fields, generated by a simple coil placed on the head, are used to stimulate a small area of the brain. A session of rTMS takes about 30 minutes; it is typically given over consecutive weekdays for several weeks, on an outpatient basis. rTMS is usually well tolerated with minimal side effects, as there is no anaesthetic, (while receiving stimulation, you are fully awake) and memory is not affected.

Electroconvulsive therapy

ECT remains one of the most effective treatments for severe depression, particularly those at risk of suicide. However, doctors usually reserve ECT for situations in which several drugs have failed, 
partly because of its technical complexity, and partly because of its negative image. It works by passing an electrical current through the brain to produce an epileptic fit – hence the name, electro-convulsive. On average, six to 12 treatments are given over 
several weeks. 

Herbs and supplements

Many people are trying supplements such as St John’s Wort which appears to raise levels of serotonin, dopamine, and norepinephrine. It would be a mistake, however, to regard it as entirely benign as it can affect the action of quite a few drugs, including the anti-clotting drug warfarin (Coumadin), the AIDS drug indinavir (Crixivan), and birth control pills. There is a possibility, too, of bad interactions with drugs such as MAOIs and SSRIs that boost serotonin.