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Chapter 1: A public health approach to mental health : Previous page | 1,2,3,4

Understanding mental health

  Chapter 1

Mental health has been defined variously by scholars from different cultures. Concepts of mental health include subjective well-being, perceived self-efficacy, autonomy, competence, intergenerational dependence, and self-actualization of one's intellectual and emotional potential, among others. From a cross-cultural perspective, it is nearly impossible to define mental health comprehensively. It is, however, generally agreed that mental health is broader than a lack of mental disorders.

An understanding of mental health and, more generally, mental functioning is important because it provides the basis on which to form a more complete understanding of the development of mental and behavioural disorders.

In recent years, new information from the fields of neuroscience and behavioural medicine has dramatically advanced our understanding of mental functioning. Increasingly, it is becoming clear that mental functioning has a physiological underpinning, and is fundamentally interconnected with physical and social functioning and health outcomes.

Advances in neuroscience

The World Health Report 2001 appears at an exciting time in the history of neuroscience. This is the branch of science which deals with the anatomy, physiology, biochemistry and molecular biology of the nervous system, especially as related to behaviour and learning. Spectacular advances in molecular biology are providing a more complete view of the building blocks of nerve cells (neurons). These advances will continue to provide a critical platform for the genetic analysis of human disease, and will contribute to new approaches to the discovery of treatments.

The understanding of the structure and function of the brain has evolved over the past 500 years (Figure 1.2). As the molecular revolution proceeds, tools such as neuroimaging and neurophysiology are permitting researchers to see the living, feeling, thinking human brain at work. Used in combination with cognitive neuroscience, imaging technologies make it increasingly possible to identify the specific parts of the brain used for different aspects of thinking and emotion.

Figure 1.2 Understanding the brain

The brain is responsible for melding genetic, molecular and biochemical information with information from the world. As such, the brain is an extremely complex organ. Within the brain, there are two types of cells: neurons and neuroglia. Neurons are responsible for sending and receiving nerve impulses or signals. Neuroglia provide neurons with nourishment, protection and structural support. Collectively, there are more than one hundred billion neurons in the brain, comprising thousands of distinct types. Each of these neurons communicates with other neurons via specialized structures called synapses. More than one hundred distinct brain chemicals, called neurotransmitters, communicate across these synapses. In aggregate, there are probably more than 100 trillion synapses in the brain. Circuits, formed by hundreds or thousands of neurons, give rise to complex mental and behavioural processes.

During fetal development, genes drive brain formation. The outcome is a specific and highly organized structure. This early development can also be influenced by environmental factors such as the pregnant woman's nutrition and substance use (alcohol, tobacco, and other psychoactive substances) or exposure to radiation. After birth and throughout life, all types of experience have the power not only to produce immediate communication between and among neurons, but also to initiate molecular processes that remodel synaptic connections (Hyman 2000). This process is described as synaptic plasticity, and it literally changes the physical structure of the brain. New synapses can be created, old ones removed, existing ones strengthened or weakened. The result is that information processing within the circuit will be changed to accommodate the new experience.

Prenatally, during childhood and through adulthood, genes and environment are involved in a series of inextricable interactions. Every act of learning ­ a process that is dependent both on particular circuits and on the regulation of particular genes ­ physically changes the brain. Indeed, the remarkable evolutionary success of the human brain is that, within certain limits, it remains plastic across the lifespan. This recent discovery of lifelong synaptic plasticity represents a shift away from earlier theories that held that the structure of the adult brain is static (see Box 1.1).

Box 1.1 The brain: new understanding wins the Nobel Prize

The Nobel Prize in Physiology or Medicine for 2000 was awarded jointly to Professor Arvid Carlsson, Professor Paul Greengard and Professor Eric Kandel for their discoveries concerning how brain cells communicate with each other.1 Their research is related to signal transduction in the nervous system, which takes place in synapses (points of contact between brain cells). These discoveries are crucial in advancing the understanding of the normal functioning of the brain, and how disturbances in this signal transduction can lead to mental and behavioural disorders. Their findings have already resulted in the development of effective new medications.

Arvid Carlsson's research revealed that dopamine is a transmitter of the brain that helps to control movements and that Parkinson's disease is related to lack of dopamine. As a result of this discovery, there is now an effective treatment (L-DOPA) for Parkinson's disease. Carlsson's work also demonstrated how other medications work, especially drugs used to treat schizophrenia, and has led to the development of a new generation of effective antidepressant medications.

Paul Greengard discovered how dopamine and a number of other neurotransmitters exert their influence in the synapse. His research clarified the mechanism by which several psychoactive medications act.

Eric Kandel showed how changes in synaptic function are central to learning and memory. He discovered that the development of long-term memory requires a change in protein synthesis which can also lead to changes in the shape and function of the synapse. By furthering understanding of the brain mechanisms crucial for memory, this research increases the possibility of developing new types of medications to improve memory functioning.

1 Butcher J (2000). A Nobel pursuit. The Lancet, 356: 1331.

As notable as discoveries to date have been, neuroscience is yet in its infancy. Future advances will provide a more complete understanding of how the brain is related to complex mental and behavioural functioning. Innovations in brain imaging along with neuropsychological and electrophysiological studies will permit real time cinema of the nervous system at work. Imaging will be combined with a growing ability to record from a large number of neurons at once; in this manner, it will be possible to decode their language. Other advances will be based on progress in genetics. An initial working draft sequence of the human genome is available in the public domain (at http://www.ornl.gov/hgmis/). One of the important uses of genomic information will be to provide a new basis for developing effective treatments for mental and behavioural disorders.

Another important tool that will enhance understanding of the molecular building blocks of development, anatomy, physiology and behaviour is the generation of genetically altered mice. For nearly every human gene there is an analogous mouse gene. This conservation of gene function between humans and mice suggests that mouse models will yield fundamental insights into human physiology and disease (O'Brien et al. 1999). Many laboratories around the world are involved in systematically inserting or deleting identified genes, and others are embarking on projects of generating random mutations throughout the mouse genome. These approaches will help connect genes with their actions in cells, organs and whole organisms.

Integration of the research results of neuroimaging and neurophysiology with those of molecular biology should lead to a greater understanding of the basis of normal and abnormal mental function, and to the development of more effective treatments.

Advances in behavioural medicine

Advances have occurred not only in our understanding of mental functioning, but also in the knowledge of how these functions influence physical health. Modern science is discovering that, while it is operationally convenient for purposes of discussion to separate mental health from physical health, this is a fiction created by language. Most "mental" and "physical" illnesses are understood to be influenced by a combination of biological, psychological and social factors. Furthermore, thoughts, feelings and behaviour are now acknowledged to have a major impact on physical health. Conversely, physical health is recognized as considerably influencing mental health and well-being.

Behavioural medicine is a broad interdisciplinary area that is concerned with the integration of behavioural, psychosocial, and biomedical science knowledge relevant to the understanding of health and illness. Over the past 20 years, mounting scientific evidence from the field of behavioural medicine has demonstrated a fundamental connection between mental and physical health (see Box 1.2). Research has shown, for example, that women with advanced breast cancer who participate in supportive group therapy live significantly longer than women who do not participate in group therapy (Spiegel et al. 1989), that depression predicts the incidence of heart disease (Ferketich et al. 2000), and that realistic acceptance of one's own death is associated with decreased survival time in AIDS, even after controlling for a range of other potential predictors of mortality (Reed et al. 1994).

Box 1.2 Pain and well-being

Persistent pain is a major public health problem, accounting for untold suffering and lost productivity around the world. While specific estimates vary, it is agreed that chronic pain is debilitating and costly, ranking among the top reasons for health care visits and health-related work absences.

A recent WHO study of 5447 individuals across 15 study centres located in Asia, Africa, Europe and the Americas examined the relationship between pain and well-being.1 Results showed that those with persistent pain were over four times more likely to have an anxiety or depressive disorder than those without pain. This relationship was observed in all study centres, regardless of geographical location. Other studies have suggested that pain intensity, disability, and anxiety/depression interact to develop and maintain chronic pain conditions.

Promisingly, a recent primary care study of 255 people with low-back pain has shown that a skills-based group intervention led by lay people reduces worries, decreasing disability.2 The intervention was based on a model of chronic disease self-management, and consisted of four two-hour classes, held once a week, with 10­15 participants per class. The lay leaders, who themselves had recurrent or chronic back pain, received two days of formal training by a clinician familiar with the treatment of back pain and the treatment programme. No significant problems arose with the lay leaders, and their capabilities in implementing the intervention were noted as impressive. This study indicates that non-health professionals can successfully deliver structured behavioural interventions, which holds promise for applications to other disease areas.

1Gureje O et al. (1998). Persistent pain and well-being: a World Health Organization study in primary care. Journal of the American Medical Association, 280(2): 147-151.

2 Von Korff M et al. (1998). A randomized trial of a lay person-led self-management group intervention for back pain patients in primary care. Spine, 23(23): 2608-2615.

How do mental and physical functioning influence each other? Research has pointed to two main pathways through which mental and physical health mutually influence each other over time. The first key pathway is directly through physiological systems, such as neuroendocrine and immune functioning. The second primary pathway is through health behaviour. The term health behaviour covers a range of activities, such as eating sensibly, getting regular exercise and adequate sleep, avoiding smoking, engaging in safe sexual practices, wearing safety belts in vehicles, and adhering to medical therapies (see Box 1.3).

Box 1.3 Adhering to medical advice

Patients do not always adhere to, or comply with, the advice of their health care providers. One review of the literature suggests that the average adherence rate for long-term medication use is just over 50%, while the adherence rate to lifestyle changes such as altering one's diet is very low. In general, the more lengthy, complex or disruptive the medical regimen, the less likely patients are to comply. Other important factors in adherence include the provider's communication skills, the patient's beliefs about the usefulness of the recommended regimen, and his or her ability to obtain medications or other recommended treatments at a reasonable cost.

Depression plays an important role in non-adherence to medical treatment. Depressed patients are three times more likely not to comply with medical regimens than non-depressed patients.1 This means, for example, that depressed diabetic patients are more likely to have a poorer diet, more frequent hyperglycemia, greater disability, and higher health care costs than non-depressed diabetics.2,3 The treatment of anxiety and depression in diabetic patients results in both improved mental and physical outcomes.4-6

The strong relationship between depression and non-adherence suggests that medical patients, particularly those who are noncompliant, should be routinely screened and, if necessary, treated for depression.

1DiMatteo MR et al. (2000). Depression is a risk factor for noncompliance with medical treatment. Archives of Internal Medicine, 160: 2101-2107.

2 Ciechanowski PS et al. (2000). Depression and diabetes: impact of depressive symptoms on adherence, function, and costs. Archives of Internal Medicine, 160: 3278-3285.

3 Ziegelstein RC et al. (2000). Patients with depression are less likely to follow recommendations to reduce cardiac risk during recovery from a myocardial infarction. Archives of Internal Medicine, 2000, 160: 1818-1823.

4 Lustman PJ et al. (1995). Effects of alprazolam on glucose regulation in diabetes: results of a double-blind, placebo-controlled trial. Diabetes Care, 18(8): 1133-1139.

5 Lustman PJ et al. (1997). Effects of nortriptyline on depression and glycemic control in diabetes: results of a double-blind, placebo-controlled trial. Psychosomatic Medicine, 59(3): 241-250.

6 Lustman PJ et al. (2000). Fluoxetine for depression in diabetes: a randomized double-blind placebo-controlled trial. Diabetes Care, 23(5): 618-623.

Although the physiological and behavioural pathways are distinct, they are not independent from one another, in that health behaviour can affect physiology (for example, smoking and sedentary lifestyle decrease immune functioning), while physiological functioning can influence health behaviour (for example, tiredness leads to forgetting medical regimens). What results is a comprehensive model of mental and physical health, in which the various components are related and mutually influential over time.

Physiological pathway

In an integrated and evidence-based model of health, mental health (including emotions and thought patterns) emerges as a key determinant of overall health. Anxious and depressed moods, for example, initiate a cascade of adverse changes in endocrine and immune functioning, and create increased susceptibility to a range of physical illnesses. It is known, for instance, that stress is related to the development of the common cold (Cohen et al. 1991) and that stress delays wound healing (Kielcot-Glaser et al. 1999).

While many questions remain concerning the specific mechanisms of these relationships, it is clear that poor mental health plays a significant role in diminished immune functioning, the development of certain illnesses, and premature death.

Health behaviour pathway

Understanding the determinants of health behaviour is particularly important because of the role that health behaviour plays in shaping overall health status. Noncommunicable diseases such as cardiovascular disease and cancer take an enormous toll in lives and health worldwide. Many of them are strongly linked to unhealthy behaviour such as alcohol and tobacco use, poor diet and sedentary lifestyle. Health behaviour is also a prime determinant of the spread of communicable diseases such as AIDS, through unsafe sexual practices and needle sharing. Much disease can be prevented by healthy behaviour.

The health behaviour of an individual is highly dependent on that person's mental health. Thus, for example, mental illness or psychological stress affect health behaviour. Recent evidence has shown that young people with psychiatric disorders, for example depression and substance dependence, are more likely to engage in high-risk sexual behaviour, compared to those with no psychiatric disorder. This puts them at risk of a range of sexually transmitted diseases, including AIDS (Ranrakha et al. 2000). But other factors also have an effect on health behaviour. Children and adolescents learn through direct experience, through information and by observing others, and this learning affects health behaviour. For example, it has been established that drug use before the age of 15 years is highly associated with the development of drug and alcohol abuse in adulthood (Jaffe 1995). Environmental influences, such as poverty or societal and cultural norms, also affect health behaviour.

Because of the recent nature of this scientific evidence, the link between mental and physical health has yet to be fully recognized and acted upon by the health care system. Yet the evidence is clear: mental health is fundamentally linked to physical health outcomes.

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