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Everything you need to know about depression

Depression has been defined as ‘the plague of the 21st century’. This is more than a catchy phrase chosen to convey how spread this mental disorder is and the fact that is spares no one. According to the World Health Organisation (WHO), depression affects about 350 million people around the world. However, this figure is only an estimate based on diagnosed cases with many more being undiagnosed. This article aims to answer some key questions about depression.

What is depression? 

Major Depressive Disorder is more commonly referred to as ‘depression’. However, depression is not a single condition. Rather, there are different types of depression, such as Seasonal Affective Disorder (SAD), Postpartum Depression, Bipolar Disorder and Atypical Depression just to mention a few.

Even though depression is an affective disorder, it should not be confused with having mood swings or showing the appropriate emotional response to unpleasant life events. It is also a common mistake to assume that depression affects only emotions as it also impairs people’s cognitive and physical abilities. Depression is a serious health condition that can affect all aspects of a person’s life, ranging from people’s ability to meet school or occupational demands to being able to fulfil family responsibilities and do domestic chores. It can even impair people’s ability to engage in social activities and have fulfilling relationships. For these reasons, depression is one of the major leading causes of disability worldwide, with severe cases leading about 1 million people to committing suicide every year.

What are the symptoms of depression?

According to the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM – V), for people to be diagnosed with depression they must have experienced either symptom 1 or 2 (see below) for at least two weeks together with four or more of the other symptoms listed below. The diagnosis is based on the effect of the symptoms on the individual compared to previous functioning (e.g. each individual has a different baseline). The symptoms of depression are as follows:

1. Depressed mood: people usually report feeling sad or empty or they are described as being tearful by others. Children and adolescents might display an irritable mood instead.

2. Loss of interest or pleasure: people often report a marked decrease in interest or pleasure in all or almost all activities previously enjoyed.

3. Significant weight loss or gain: the weight change is not caused by the adoption of a new dietary regime and must be more than 5% of normal body weight in a month. People might otherwise report a decrease or increase in appetite. On the other hand, children might fail to gain weight as expected.

4. Sleep disturbances: these can manifest either as insomnia (difficulties in falling or staying asleep) or hypersomnia (sleeping for long periods of time).

5. Psychomotor agitation or retardation: this is more than a subjective feeling of restlessness or of being slowed down and is observable by others.

6. Fatigue or loss of energy: people frequently report feeling tired and being sluggish. This leads to markedly reduced activity levels.

7. Feelings of worthlessness or excessive or inappropriate guilt: these feelings are often delusional in that they do not reflect reality.

8. Diminished ability to think or concentrate: impairments in cognitive function can also manifest in terms of indecisiveness.

9. Recurrent thoughts of death: these are different from the fear of dying but are more along the lines of recurrent suicidal ideation, with or without a specific plan, or actual suicidal attempts.

These symptoms must be present nearly every day and should not be attributable to substance or drug abuse, or to medication. The number and severity of the symptoms together determine whether the depressive episode is classified as mild, moderate or severe. The greater the severity of the episode, the greater the impairment the person will suffer in terms of being able to carry on with life as normal.

What causes depression?

The interplay of biological, physiological, psychological and social factors in the development of depression is generally acknowledged. No single factor or set combination of factors necessarily leads to the development of depression. Instead, as the diathesis stress model proposes, people might have a vulnerability (or diathesis) to developing depression which is triggered by stressful events in the environment.

Biological vulnerability suggests that there are some genetically inherited factors that can increase the likelihood of developing depression. One such example is abnormal brain chemistry: depression has consistently been associated with low levels of the neurotransmitter serotonin which is implicated in maintaining both emotional and mental health. For more information about the role that serotonin and other neurotransmitters play in depression click here. Research has also shown that depression runs in families: therefore, having one family member with the disorder increases one’s chances of developing the disorder compared to the rest of the population. Moreover, personality-related factors can increase vulnerability to depression. Characteristics such as low self-esteem and the tendency to be overly critical might be inherited from one’s parents or might develop as a consequence of early life experiences. These personality traits are associated with a greater chance of developing depression.

Physiological vulnerability emphasises the connection between some physical conditions or illnesses and the chance of developing depression. For instance, research has shown that there is a mutually causal relationship between life-threatening illnesses such as cardiovascular disease and cancer and the chance of developing depression. Similarly, the relationship between intestinal toxemia, an infection that develops as a consequence of products absorbed by the digestive tract, was identified as early as 100 years ago. Research has shown that even vitamin B6 and B12 deficiency can lead to depression. These examples show that one’s physiological health is closely connected to one’s mental health, and this interrelatedness should not be underestimated.

Psychological vulnerability indicates that there are social factors that can increase the chance of developing depression.For example, depression can be caused by loneliness. Research on both animals and humans has shown that those who become isolated from other members of their group soon begin to develop depression-like symptoms. Another article has emphasised the importance of family and friends in maintaining one’s mental wellbeing.

Cognitive vulnerability refers to one’s cognitive style. This is the way in which one processes information, thinks, faces problems and finds solutions. People who have a tendency to engage in irrational thinking are more at risk of developing depression. Irrational thinking is an automatic and therefore very quick processing mode based on past experiences: a negative experience will bias the person against similar or identical situations in the future. For example, the fact that one relationship failed might lead an individual to believe that all other relationships will consequently fail and deter him from trying a new relationship in the future. This in its turn might lead to loneliness and eventually depression. Self-esteem, the beliefs that an individual holds about himself, is a risk factor in the development of depression. Research has shown that people with low-self esteem have a greater tendency to have depressive thoughts than people with high self-esteem.

How can depression be treated?

The reassuring news is that even in its most severe forms, depression can be treated successfully, with early detection leading to higher success rates. However, people who are affected cannot simply pull themselves together or wish the illness away. Depending on the severity of depression, people should consider taking antidepressant medication and undergoing psychological or talking therapy. Keeping physically active with regular exercise and eating a healthy diet can also contribute to increased wellbeing.

About Francesca Stregapede

After pursuing a degree in Psychology, I further explored the relationship between neurochemistry and behaviour in a Masters in Brain Imaging and Cognitive neuroscience. I write about various areas of Psychology as well as articles at the interface between Neuroscience and Nutrition as I believe that nutrition has a huge impact not only on our physical wellbeing but also on our psychological states.

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