Types, Causes and  Symptoms of Depression:

Whilst we all feel sad, moody, or low from time to time, people can experience these feelings intensely, for long periods of time (weeks, months or even years) and sometimes for no apparent reason. Depression is more than just low mood, it's a serious illness that has an impact on both physical and mental health. Antidepressants are commonly prescribed, but do they address the underlying causes? There are different types of depression and each is treated differently depending on the cause of depression. Let us understand all this in detail.,

This webpage provides psychoeducation about depression; consequently, lifestyle and nutritional factors come up in the research about causes of depression, Although Psychologists at the clinic endorse a multimodal approach regarding treatment of depression, they do not make recommendations about diet and nutrition. If needed they will recommend that you consult a dietician or nutritionist. 

Types of Depression

There are types of depressive disorders. Symptoms range from relatively minor, to severe and functionally disabling. It is helpful to be aware of the range of depressive disorders and their specific symptoms.

Major Depression

Major depression (also called major depressive disorder) is characterized by persistent low mood, loss of interest or pleasure in usual activities, and significant interference with daily functioning for at least two weeks. The diagnosis is based on criteria outlined in the DSM-5, requiring at least five symptoms such as changes in appetite, sleep, fatigue, feelings of worthlessness, or thoughts of death (Hasin et al., 2018; Kennedy, 2008).

Melancholia

Melancholic depression is a severe subtype of major depression, marked by a profound loss of pleasure in almost all activities and observable psychomotor disturbances (e.g., slowed movement). This form is associated with distinct clinical features and often requires tailored treatment approaches (Gili et al., 2012; Parker et al., 2013).

Psychotic Depression

Psychotic depression involves major depressive episodes with features of psychosis, such as hallucinations (false sensory perceptions) or delusions (fixed, false beliefs). These symptoms are usually mood-congruent and can complicate treatment. Combined pharmacological approaches are often required (Dubovsky et al., 2021).

Antenatal & Postnatal Depression

Women are at increased risk for depression during pregnancy (antenatal) and after childbirth (postnatal). Research has shown that omega-3 fatty acid deficiency is associated with higher risk for perinatal depression, and supplementation may help reduce symptoms in this population (Vaz et al., 2017; Mocking et al., 2020; Zhang et al., 2020).

Bipolar Depression

Bipolar disorder involves alternating episodes of depression and mania (elevated mood, increased activity, decreased need for sleep), separated by periods of normal mood. It is closely linked to family history and sometimes misdiagnosed as other psychiatric disorders. Accurate diagnosis often depends on identifying manic episodes (Kennedy, 2008).

Cyclothymic Disorder

Cyclothymic disorder is a milder, chronic form of bipolar disorder, marked by ongoing fluctuations between hypomanic and depressive symptoms for at least two years, never reaching full criteria for mania or major depression (Hasin et al., 2018).

Dysthymic Disorder

Dysthymia (persistent depressive disorder) consists of less severe, but longer-lasting depressive symptoms compared to major depression, with a duration of at least two years (Kennedy, 2008).

Seasonal Affective Disorder (SAD)
SAD is a depressive disorder with a seasonal pattern, typically occurring during winter months when sunlight exposure is reduced. It is thought to relate to vitamin D deficiency and is commonly treated with light therapy or vitamin D supplementation (Kennedy, 2008).

Causes of Depression

There are many causes for depression, and overall depression occurs when your capacity to cope with stressors is impaired. When that capacity is completely overwhelmed, a sense of hopelessness evolves sometimes leading to suicidal ideation.  It is vital not to let the day to day hassles and stresses  lead to overwhelm

Adverse Life Events:

Chronic stressors such as unemployment and abusive relationships increase the risk of depression, though acute negative events can also trigger episodes in genetically or biologically vulnerable individuals (Kessler et al., 2003).

Personal Factors:

Family history is a significant risk factor, but environmental influences and nutrient deficiencies also contribute (Hasin et al., 2018). Personality traits like low self-esteem and high self-criticism increase vulnerability.

Abnormal Brain Activity:

Contrary to the "chemical imbalance" hypothesis, depression is now understood to involve multiple neurophysiological disturbances identifiable with advanced brain imaging (Kendler, 2016). Neuroscientific research using quantitative electroencephalography (QEEG) has advanced our understanding of depression beyond the old "chemical imbalance" model. QEEG studies repeatedly show that depression is associated with diverse brain-based patterns, including but not limited to:

• Low power in low frequency bands: Depressed individuals may show abnormalities in low-frequency EEG power, which can be detected and quantified using QEEG (Morgan et al., 2005).
• Elevated alpha waves and frontal alpha asymmetry: Frontal alpha asymmetry is one of the most widely studied QEEG markers in depression, with evidence indicating that individuals with depression often show greater right than left frontal alpha activity. This asymmetry is considered a stable trait marker and may reflect underlying vulnerability to depression (Van Der Vinne et al., 2017; Gotlib, 1998; Xie et al., 2023).
• Excessive fast waves (beta) and globally low power levels: QEEG has identified patterns such as alterations in beta activity and overall reduced power across multiple EEG bands in those with major depressive disorder (Knott et al., 2001; Kopańska et al., 2022).
• Multiple distinct QEEG subtypes: Rather than a single biomarker, QEEG reveals that depression can manifest with several distinct patterns of brain activity, including combinations of the above features and abnormal functional connectivity (Leuchter et al., 2012; Hunter et al., 2010).

This growing body of evidence demonstrates that depression is characterised by a range of brain-based abnormalities detectable with QEEG, supporting a more nuanced and individualised understanding of its neurobiology.

Signs and Symptoms

Clinical diagnosis requires at least two weeks of core symptoms (low mood, loss of interest/pleasure), plus additional symptoms such as sleep disturbance, appetite change, low energy, poor concentration, or thoughts of worthlessness or suicide (Hasin et al., 2018).

Behaviours During Depression

• not going out anymore
• not getting tasks done at work/school
• withdrawing from close family and friends
• having an alcohol or drug dependence
• not partaking in activities that they usually find enjoyable
• unable to concentrate

Feelings During An Episode of Depression

• overwhelmed
• guilty
• irritable
• frustrated
• lacking in confidence
• unhappy
• indecisive
• disappointed
• miserable
• sad

Thoughts During Depression

• 'I’m a failure.'
• 'It’s my fault.'
• 'Nothing good ever happens to me.'
• 'I’m worthless.'
• 'Life’s not worth living.'
• 'People would be better off without me.'

Physical Symptoms During Depression

• chronically tired
• sick and run down
• headaches and muscle pains
• churning gut
• sleep problems
• loss or change of appetite
• significant weight loss or gain

Updated on:   21/02/2026 by: Dr. Jacques Duff – BA Psych; Grad Dip Psych; PhD; MAPS; MECNS; MAAAPB; MISNR; FANSA
Reviewed on: 21/02/2026 by: Bernard Ferriere - BA; Grad Dip App Psych; Dip Clinical Hypnosis; FCCP; MAPS; MASH; Clinical Psychologist