Major Depressive Disorder (MDD)

Definition | Aetiology | Risk Factors | Clinical Presentation | Investigations | Management | When to Refer | References

Definition

Major Depressive Disorder (MDD), also known as clinical depression, is a common and serious mental health condition characterised by persistent feelings of sadness, hopelessness, and a lack of interest or pleasure in daily activities. It can significantly impair daily functioning, relationships, and quality of life. MDD is a chronic condition that often requires long-term treatment and management.

Aetiology

The exact cause of MDD is not fully understood, but it is believed to result from a combination of genetic, biological, environmental, and psychological factors:

• Genetic Factors: A family history of depression or other mood disorders increases the likelihood of developing MDD.
• Neurochemical Imbalance: Dysregulation of neurotransmitters such as serotonin, norepinephrine, and dopamine is thought to contribute to depressive symptoms.
• Hormonal Changes: Hormonal imbalances, such as those occurring during pregnancy, postpartum, or menopause, can trigger or exacerbate depression.
• Environmental Factors: Stressful life events, such as trauma, loss of a loved one, or financial difficulties, can act as triggers for depression.
• Psychosocial Factors: Personality traits such as low self-esteem, pessimism, or chronic stress may increase vulnerability to MDD.

Risk Factors

Several factors increase the likelihood of developing MDD:

• Family History: Having a first-degree relative with depression or another mood disorder increases the risk.
• Gender: Women are more likely to be diagnosed with MDD than men, potentially due to hormonal, psychological, and sociocultural factors.
• Previous Episodes: A history of previous depressive episodes increases the risk of recurrence.
• Chronic Illness: Conditions such as diabetes, heart disease, or chronic pain can contribute to the development of MDD.
• Substance Abuse: The use of drugs or alcohol can trigger or worsen depressive symptoms and complicate treatment.
• Childhood Trauma: Early life experiences such as abuse, neglect, or significant loss can increase vulnerability to depression later in life.

Clinical Presentation

MDD presents with a range of psychological and physical symptoms that persist for at least two weeks and significantly impact daily functioning:

Psychological Symptoms

• Low Mood: Persistent feelings of sadness, emptiness, or hopelessness.
• Anhedonia: Loss of interest or pleasure in activities that were once enjoyable.
• Guilt and Worthlessness: Excessive feelings of guilt, worthlessness, or self-blame.
• Cognitive Impairment: Difficulty concentrating, making decisions, or thinking clearly.
• Suicidal Thoughts: Thoughts of death, suicide, or self-harm, which may be passive or active.

Physical Symptoms

• Fatigue: Persistent tiredness and lack of energy, even after adequate rest.
• Sleep Disturbances: Insomnia (difficulty falling asleep or staying asleep) or hypersomnia (excessive sleeping).
• Appetite Changes: Significant weight loss or gain due to changes in appetite, often leading to overeating or loss of interest in food.
• Psychomotor Agitation or Retardation: Restlessness, pacing, or slowed physical movements and speech.
• Physical Pain: Unexplained physical symptoms such as headaches, stomachaches, or chronic pain.

Investigations

The diagnosis of MDD is primarily clinical, based on a detailed history and mental health assessment. Additional investigations may be conducted to rule out other conditions:

• Psychiatric Assessment: A thorough mental health evaluation, often using structured interviews or diagnostic tools such as the Patient Health Questionnaire-9 (PHQ-9).
• Medical History and Physical Examination: A complete medical history and physical examination to rule out underlying medical conditions that could mimic depressive symptoms.
• Laboratory Tests: Blood tests such as thyroid function tests, full blood count (FBC), and electrolyte levels to exclude physiological causes of depression, such as hypothyroidism.
• Imaging Studies: MRI or CT scans may be considered if there are neurological symptoms or if there is a need to rule out brain lesions or structural abnormalities.

Management

The management of MDD involves a combination of pharmacological treatments, psychological therapies, and lifestyle modifications:

Pharmacological Treatments

• Selective Serotonin Reuptake Inhibitors (SSRIs): Common first-line medications for MDD, such as sertraline, fluoxetine, and citalopram.
• Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): Medications such as venlafaxine and duloxetine, used when SSRIs are ineffective or not well tolerated.
• Tricyclic Antidepressants (TCAs): Older antidepressants like amitriptyline, used in treatment-resistant cases or for specific symptoms such as chronic pain.
• Atypical Antidepressants: Medications such as mirtazapine and bupropion, which work differently from SSRIs and SNRIs.
• Monoamine Oxidase Inhibitors (MAOIs): Rarely used due to dietary restrictions and potential side effects but may be considered in treatment-resistant cases.

Psychological Therapies

• Cognitive Behavioural Therapy (CBT): A widely used therapy that helps patients identify and change negative thought patterns and behaviours.
• Interpersonal Therapy (IPT): Focuses on improving relationships and resolving interpersonal issues that may contribute to depression.
• Mindfulness-Based Cognitive Therapy (MBCT): Combines mindfulness techniques with cognitive therapy to prevent relapse in recurrent depression.
• Psychodynamic Therapy: Explores underlying emotional conflicts and their influence on current behaviour and mood.

Lifestyle Modifications

• Regular Exercise: Physical activity can help alleviate depressive symptoms by releasing endorphins and improving overall well-being.
• Healthy Diet: A balanced diet with adequate hydration can support mental health. Reducing caffeine, sugar, and alcohol intake may help minimise symptoms.
• Sleep Hygiene: Establishing a regular sleep routine and creating a restful environment can improve sleep quality and reduce depressive symptoms.
• Stress Management: Techniques such as mindfulness, meditation, and relaxation exercises to manage stress and improve mood.
• Social Support: Encouraging patients to seek support from friends, family, or support groups can be beneficial in managing depression.

When to Refer

Referral to a specialist mental health service or psychiatrist is necessary in the following situations:

• Severe or treatment-resistant depression that does not respond to initial therapies or requires more intensive management.
• Presence of co-occurring mental health conditions, such as anxiety disorders, substance use disorders, or personality disorders.
• Risk of suicide, self-harm, or harm to others, necessitating urgent intervention and possible hospitalisation.
• Need for specialised psychological therapies, such as CBT or IPT, that are not available in primary care settings.

References

1. NHS (2024) Clinical Depression. Available at: https://www.nhs.uk/conditions/clinical-depression/ (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Depression in Adults: Treatment and Management. Available at: https://www.nice.org.uk/guidance/cg90 (Accessed: 26 August 2024).
3. British Medical Journal (2024) Major Depressive Disorder: Clinical Review. Available at: https://www.bmj.com/content/350/bmj.h3773 (Accessed: 26 August 2024).

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