Mood disorders

Mood Disorders Overview

Professor: Riccardo BrambillaCourse Code: BI3451Date: 1 November 2024Affiliation: Neuroscience Division - School of Biosciences & Neuroscience and Mental Health Innovation Institute

Learning Outcomes

Understanding Diagnostic Symptoms:

• Major Depressive Disorder (MDD): A severe mood disorder characterized by a persistent feeling of sadness or a lack of interest in previously enjoyed activities.

• Bipolar Disorder (BD): A mental health condition marked by extreme mood swings, including emotional highs (mania or hypomania) and lows (depression).

• Anxiety Disorders: A group of disorders characterized by excessive and persistent fear or anxiety impacting daily functions.

Acquiring Genetic Basis Knowledge for MDD

Explore the heritability of MDD, which is influenced by various genetic factors, along with environmental contributors such as trauma and stress.

Recognizing Brain Regions' Roles:

Understanding the brain areas involved in mood regulation is essential for developing neuromodulatory treatment approaches. Specific brain regions to focus on include:

1. Prefrontal Cortex: Regulates higher-order cognitive functions and emotions.

2. Amygdala: Plays a key role in processing emotions such as fear and pleasure.

3. Hippocampus: Involvement in memory and emotional regulation is significant in mood disorders.

Appreciating Neural Circuitry:

Recognize the importance of neural pathways involved in MDD, Anxiety, and PTSD, focusing on how these connections influence symptoms and treatment responses.

Comprehending Animal Models:

Understanding the rationale behind various animal models of depression and anxiety is crucial for developing and testing potential treatments. These models provide insights into the biological and behavioral symptoms akin to human mental disorders.

Disability Associated with Mental Disorders

Statistics on Disability:

• Mental Disorders: Account for 20.1% of Disability-adjusted life years (DALYs).

• Anxiety Disorders: Contribute 4.2% to this statistic.

• Comparison with Neurological Disorders: Together, neurological disorders and other diseases account for 75.2% of DALYs.

• Data Source: Craske et al (2017)

Classification of Mood Disorders

Reference: Molecular Neuropharmacology, Fourth Edition, 2020

• Mood disorders are categorized based on a range of symptoms and emotional disturbances.

• Types of Mood Disorders:

  • Unipolar Depression: Characterized by episodes of major depression without the manic phases of bipolar disorder.

  • Bipolar Disorder: Involves alternating periods of depressive episodes and manic episodes.

  • Dysthymia (Persistent Depressive Disorder): A chronic form of depression lasting for at least two years.

  • Cyclothymia: A milder form of bipolar disorder with periods of hypomanic symptoms and depression lasting for at least two years (1 year in children).

Symptoms of Mood Disorders

Manic Episodes:

• Duration: At least 1 week or any duration if hospitalized.

• Symptoms Include:

  • Elevated mood or irritability

  • Inflated self-esteem or grandiosity

  • Decreased need for sleep

  • Increased talkativeness or pressured speech

  • Flight of ideas or racing thoughts

  • Distractibility

  • Engaging in high-risk activities without regard for consequences

• Severity: Symptoms must cause marked impairment in functioning or necessitate hospitalization.

Major Depressive Episodes:

• Duration: Must last for a two-week period with at least five specific symptoms present.

• Core Symptoms Includes:

  • Depressed mood most of the day, nearly every day

  • Anhedonia (marked diminished interest or pleasure in all or almost all activities)

  • Significant weight loss when not dieting, weight gain, or changes in appetite

  • Insomnia or hypersomnia (excessive sleep)

  • Psychomotor agitation or retardation

  • Fatigue or loss of energy

  • Feelings of worthlessness or excessive guilt

  • Diminished ability to think or concentrate

  • Recurrent thoughts of death or suicide

• Outcome: Symptoms must cause clinically significant distress or impairment in social, occupational, or other areas of functioning.

Anxiety Disorders Overview

Comorbidity:

• Anxiety disorders frequently co-occur with depressive disorders, complicating diagnosis and treatment.

Major Diagnostic Features:

• Separation Anxiety Disorder: Characterized by excessive fear of being apart from attachment figures.

• Panic Disorder: Features recurrent, unexpected panic attacks followed by worry over future attacks.

• Specific Phobias: Involves marked fear or anxiety about specific objects or situations, leading to avoidance behaviors.

• Generalized Anxiety Disorder (GAD): Defined by excessive anxiety and worry about a variety of events or activities, occurring most days for at least six months.

Epidemiology of Mood Disorders

Depression:

• Prevalence: Approximately 3.8% of the population experiences major depression during their lifetime, with current rates significantly increasing (estimated 20%).

• At-Risk Groups: Higher prevalence observed in women (twice the rate as men) and those aged between 20-40 years. A family history of mood disorders also increases risk.

Bipolar Disorder:

• Lifetime Prevalence: Estimated between 2-4%.

• Risks: Individuals face increased risk for suicide and reduced life expectancy associated with this disorder.

Neurobiology of Major Depressive Disorder (MDD)

Brain Regions Involved:

1. Nucleus Accumbens: Integral in reward perception and processing.

2. Amygdala: Involved in fear response and the integration of memory and emotion.

3. Medial Prefrontal Cortex: Key site of executive control and emotional regulation.

4. Lateral Habenula: Associated with negative salience and the regulation of mood.

Neurotransmitters:

• Imbalances in Neurotransmitters: Dysregulation of key neurotransmitters such as serotonin, norepinephrine, and dopamine has significant implications for mood disorders and their treatment.

Treatment and Models in Research

Animal Models:

• Established Based on Validities: Models used in research are defined by face validity (resemblance to human condition), construct validity (represent underlying mechanisms), and predictive validity (ability to predict treatment effects).

• Common Models: Include chronic mild stress models, forced swim tests (FST), and tail suspension tests (TST) that serve in understanding depression and anxiety mechanisms.

Neuromodulation Techniques:

• Current research is exploring various brain stimulation techniques for efficacy in treating MDD and anxiety disorders.

• Future Directions: Emphasizes the need for personalized approaches in neuroimaging and standardized diagnosis to improve treatment outcomes.

References

• Numerous notable studies and meta-analyses have been cited to support the discussions on the symptoms, neurobiology, and treatment strategies for mood disorders.