Central nervous system 1 – mood disorders

Central nervous system 1 – mood disorders

Alan Nimmo

Key Topics

  • Introduction to mood disorders
  • Unipolar depression and its clinical management
  • Bipolar disorder and its clinical management
  • Anxiety disorders and their clinical management

Learning Objectives

  • Be familiar with the common signs and symptoms associated with mood disorders
  • Be familiar with the common therapies used to manage depression, and the impact they have both on oral health and the safe management of dental patients
  • Be familiar with the common therapies used to manage anxiety disorders, and the impact they have both on oral health and the safe management of dental patients
  • Be familiar with the issue of anxiety associated with dental therapy


The central nervous system (CNS) is the most complex of all our organ systems, and how it functions is only beginning to be understood. However, drugs that have effects on the central nervous system are some of the most commonly prescribed medications.

There is also a wide range of CNS disorders that may cause oral symptoms or impact on a patient’s oral health, oral hygiene and their management in the dental clinic. Also, neurodegenerative disorders, such as Alzheimer’s disease, represent a growing concern, particularly with our aging populations, while strokes represent the leading cause of adult disability.

A simple classification of psychological disease is shown in Table 13.1.

Table 13.1 A simple classification of psychological disease

Mood disorders Psychosis Personality disorders
Anxiety Organic (delirium tremens, dementia) Psychopathy
Depression Functional (schizophrenia, psychotic depression)

Mood disorders are characterized by exaggerated normal responses such as extreme or inappropriate anxiety or obsessive behaviour. In contrast, psychotic disorders are characterized by abnormal and bizarre thought processes. Depression is primarily a mood disorder, but there is a subtype which includes a psychotic component (psychotic depression). Both mood- and psychotic disorders may respond to therapeutic intervention, but personality disorders are not responsive.

This chapter will examine two of the most common CNS disorders, depression and anxiety, the medications used to manage them, and the implications for dental practice. Together, depression and anxiety are referred to as mood, or affective, disorders. It is likely that more than 1 in 4 people will experience one or both of these conditions at some point during their lives.


Clinical features

Depression is a very common mood disorder, affecting close to 1 in 5 individuals at some point in their lifetime.

All people experience feelings of sadness, loneliness and grief at some points in their lives. These represent natural human emotions in response to life events. In general, people can still function normally while they have these feelings, and they have a sense they will get over these feelings. However, clinical depression, or major depressive disorder, is considered to occur when these feelings persist for longer than normal, are excessive, or are occurring in the absence of any obvious external trigger. Also, depression is a major contributing factor to suicide.

Symptoms may be chronic or episodic. In addition, clinical depression is accompanied by physical, or biological, signs. The defining symptoms are shown in Table 13.2.

Table 13.2 The defining symptoms of depression

Emotional symptoms Biological symptoms
Sadness and apathy
Reduced capacity to experience pleasure
Lowered self-esteem
Emotional lability (e.g. anxiety)
Reduced motivation
Poor concentration and memory
Retardation of thought
Loss of libido
Sleep disturbance especially early morning wakening
Changes in appetite and/or body weight
Reduced pain tolerance
Lowered energy levels

Early morning wakening arises due to agitation and anxiety despite persistent tiredness. A lower pain threshold may encourage susceptibility to chronic facial pain.

There are two distinct types of depression: unipolar and bipolar depression. Unipolar depression is the more common form. Here the mood swings are always in the same direction, ranging from a normal mood state to feeling depressed.

The development of unipolar depression can be reactive, occurring in response to some life event or traumatic experience, and chronic stress is considered to be a major risk factor. This type is regarded as a neurosis. However, it may also arise through endogenous events, where no external trigger can be identified. As with bipolar depression, endogenous unipolar depression may exhibit a hereditary tendency. However, approximately 75% of cases of are non-familial, and reflect stressful life events.

With bipolar depression, which affects approximately 2.5% of the population, the mood swings can alternate between feelings of depression and periods of mania. Mania can be associated with a variety of emotions, including irritability, impatience and aggression, and may sometimes include grandiose delusions. It may, therefore, be regarded as having a psychotic component.

A number of factors may impact on oral health. Suffers may neglect routine oral health practices, they may make poor nutritional choices, resorting to ‘comfort’ foods, and may avoid routine dental care. In addition, drug-induced xerostomia is an issue with many antidepressant medications.

Recently, evidence has emerged of a mechanistic link between oral and systemic disease, and depression. It is recognized that chronic stress represents a major risk factor for depression. This led to a hypothesis that the body’s response to stress may result in an immune response, and associated release of pro-inflammatory cytokines. It is this pro-inflammatory state that may mediate the behavioural changes. Hence, there is a two-way process: poor oral health, and the associated inflammation, may be a risk factor for depression, while the effective management of depression may improve oral health.

Neurochemical basis of depression

Clinical depression is considered to arise from a neurochemical imbalance in the brain. The broadly accepted theory to explain depression suggests it is associated with a deficiency in the activity of noradrenaline and/or serotonin in the brain.

Drugs that enhance the activity of noradrenaline and/or serotonin, such as tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), will elevate mood and alleviate the symptoms of depression. However, antidepressant drugs will increase the activity of noradrenaline and serotonin almost immediately, but the anti-depressant effects of these drugs may take weeks or months to fully develop. It is considered the anti-depressant effects of these drugs are associated with adaptive changes within the brain, rather than their direct, pharmacological effects. Deficiencies in serotonin are thought to be primarily responsible for the emotional symptoms, whilst deficiencies in noradrenaline correlate with the biological symptoms.

Antidepressant drug treatment

Individuals with mild depression are unlikely to benefit from antidepressant medication, whilst those with mild-to-moderate depression they may be more effectively treated by non-drug approaches, such as cognitive-behaviour therapy and exercise. Therapeutic approaches are indicated for moderate to severe major depressive disorder, but still the response to treatment will be greater if combined with the non-drug approaches.

Unipolar depression – drug treatment

The main types of antidepressant drugs used for the management of unipolar depression are discussed in the following sub-sections.

Serotonin and noradrenaline reuptake inhibitors (SNRIs):

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Aug 15, 2017 | Posted by in Orthodontics | Comments Off on Central nervous system 1 – mood disorders
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