Neurobiology of drug addiction

Question 1

Overview of the problem

Answer 1

Drug addiction is a serious chronic relapsing brain disorder.

Scope of the Problem

• Prevalence: According to the WHO, about 275 million people or roughly 5.6% of the global population aged 15-64 used drugs at least once in 2020. The prevalence of drug use disorders was estimated at 36 million people worldwide.
• Economic Impact: Drug addiction costs the UK approximately £65 billion annually, indicating a severe financial strain on public health and social services

Consequences

• Social consequences: Antisocial or criminal behaviour and family service costs. Stigmatisation results in social isolation of drug addicts. Governments should spend more money on psychosocial support.
• Physical Health: Drug abuse can lead to a myriad of health problems, depending on the substance, including cardiovascular disease, stroke, cancer, HIV/AIDS, hepatitis, lung disease, and mental disorders
• Mental Health: Depression, anxiety and schizophrenia. Bidirectional relationship where substance abuse can exacerbate or contribute to the onset of mental health issues, and vice versa

Question 2

Understand the Definition of Addiction

Answer 2

Psychological Definition

Addiction is characterised by a loss of control over behaviour, intense cravings for the addictive substance or activity, and continued involvement with it despite harmful consequences.

This article discusses addiction as a brain disease and its implications for treatment, emphasizing the psychological aspects (Volkow, Koob and McLellan, 2016).

Biological Definition

A brain disease triggered by environmental and genetic factors that cause changes in the brain’s structure and function. These changes affect the brain’s reward system, notably through neurotransmitters like dopamine. Over time, repeated exposure to addictive substances or behaviours leads to neuroadaptive changes, making the brain more reliant on the substance to trigger pleasure and less sensitive to natural rewards

Nestler explores how addictive substances can alter the brain’s neurocircuitry, leading to long-term changes in behavior and cognition. (Nestler, 2013)

Behavioural Definition

Addiction manifests as a pattern of use that typically begins with experimentation or voluntary use and progresses to regular use, risky use and finally dependency. This progression is often accompanied by an increase in tolerance and withdrawal symptoms

Leshner outlines addiction as a chronic, relapsing disorder that results from the prolonged effects of drugs on the brain (Leshner, 1997).

Social and Economic Defintion

Addiction impacts not only the individual but also their family, community, and society at large. It is associated with increased healthcare costs, loss of productivity, increased crime, and significant social stigma.

This research quantifies the economic impacts of alcohol addiction, providing insight into broader social and economic consequences(Sacks et al., 2015).

Medical Definition

Medically, addiction is defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a “substance use disorder,” characterized by a cluster of cognitive, behavioural, and physiological symptoms indicating that an individual continues using the substance despite significant substance-related problems.

DSM-5 provides the medical criteria for diagnosing substance use disorders, detailing the symptoms and behaviours that characterize addiction (American Psychiatric Association., 2013).

Stages of Addiction

1. Experimentation
2. Regular Use
3. Risky Use/Abuse. Use becomes more frequent and starts to impact the individual negatively
4. Dependence. At this stage, the individual experiences tolerance and withdrawal symptoms, indicating physical dependence
5. Addiction. Dependence coupled with a complete loss of control over use, compulsive behaviour and continued use despite understanding the negative consequences.

(Doweiko, 2015)

Question 3

Describe the addiction stages (tolerance, dependence)

Answer 3

Tolerance

A physiological state where the response to a drug decreases after repeated use, compelling the user to consume larger doses to achieve the same effect originally produced by smaller amounts

• Neuroadaptive Changes: Prolonged exposure to a drug incudes changes in the brain’s neurochemistry and receptor densities.
• Enzymatic Induction: The body may also increase the rate at which the drug is metabolised, effectively reducing its concentration in the system and requiring higher doses to maintain effect

(VolKow et al ., 2004)

Dependence

Characterised by the body’s physiological adaption to the constant presence of a drug. Marked by the onset of withdrawal symptoms

• Physical Dependence: When the body has adapted to the drug’s presence to the point that its physiological functioning is impeded without it. Withdrawal symptoms may include nausea, pain, seizures.
• Psychological Dependence: Emotional-motivational withdrawal symptoms, such as cravings, anxiety, or depression.

(Koob & Le moal, 2005)