Clinician’s Q+A – What are the root causes of drug addiction?

Drug addiction is a complex, multifaceted condition that, viewed through a clinical lens, requires a nuanced understanding of its origins. Clinicians and healthcare professionals must consider a range of biological, psychological, and social factors when evaluating substance use disorder (SUD). 

Because despite advancements in recent years, stigma does still exist1. Addiction is not a failure of willpower, lack of sense, or absence of morality. Rather, it is a chronic disease that affects the brain function and behaviour of millions around the world2. 

In terms of the UK, the latest statistics paint a concerning picture. To that point:

• Almost two in every hundred adult citizens are considered “frequent” drug users3
• Over 3% of adults in England exhibit signs of drug dependence4
• Cannabis, powder cocaine, ecstasy, hallucinogens, and amphetamines are the most commonly consumed drugs5 among 16-59 year olds
• The value of the illicit drugs market in the UK is estimated to be £9.4 billion6

This Q&A explores the root causes of drug addiction, providing insights for medical professionals working in addiction treatment and mental health. If you know someone who may be living with substance misuse, don’t hesitate to make a referral today. 

Q: What are the root causes of drug addiction? 

→ Addiction arises from an interplay of genetic, environmental, and psychological factors, each of which contributes to an individual’s vulnerability to substance dependence.

A: Drug addiction is rooted in biological, psychological, & environmental factors

Research suggests that approximately 40-60% of a person’s vulnerability to addiction is attributable to genetic factors7, as variations in genes affecting dopamine receptors can influence an individual’s risk of developing substance dependence. Environmental factors, including influences like adverse childhood experiences (ACEs), domestic violence, and social or reputational pressures, also play a significant role. 

Psychological conditions such as anxiety, depression, and trauma increase susceptibility, as individuals may turn to substances as a maladaptive coping mechanism. Chronic drug use alters brain structure, particularly in areas regulating decision-making, impulse control, and reward processing, reinforcing compulsive behaviour patterns and increasing the likelihood of relapse.

Q: Why do people become addicted? 

→ People develop addictions due to a combination of neurobiological changes, psychological predispositions, and environmental influences that reinforce substance-seeking behaviour.

A: Due to changes in the mechanism of dopamine & reward pathways

Substances like opioids, cocaine, and alcohol hijack the brain’s reward system8, flooding it with dopamine and creating intense sensations of pleasure or euphoria. Over time, the brain adapts by reducing natural dopamine production, leading to tolerance and dependency. Individuals with preexisting mental health conditions, such as depression or PTSD, are particularly vulnerable, as they may rely on substances to regulate mood and alleviate emotional pain. 

Additionally, repeated drug use strengthens neural pathways associated with craving and compulsive behaviour9, making cessation increasingly difficult without medical intervention and behavioural therapy.

Q: Are some drugs more addictive than others? Which are the most dangerous? 

→ Yes, some substances have a higher addictive potential than others, due to their impact on neurochemical pathways, particularly dopamine regulation.

A: Yes. Those substances that rapidly alter brain chemistry & reinforce compulsive use are the most addictive

Drugs such as heroin, cocaine, methamphetamine, and nicotine are among the most addictive10, as they create intense dopamine surges, reinforcing reward-seeking behaviour. Studies indicate that heroin increases dopamine levels in the brain’s reward system by up to 200%, leading to rapid dependence11. Similarly, methamphetamine’s neurotoxic effects can cause irreversible cognitive damage. Alcohol and benzodiazepines, while legal, also pose severe addiction risks due to their depressant effects and withdrawal dangers. 

Q: Can drug addiction run in families?

→ Yes, both genetic and environmental factors contribute to intergenerational addiction risk, influencing susceptibility to substance use disorders.

A: Addiction risk is shaped by both heredity and learned behaviours within family environments

Research suggests that genetics represent around half of an individual’s vulnerability to addiction. Variations in dopamine receptors (such as the DRD2 gene) may predispose individuals to compulsive substance-seeking behaviour12. 

However, familial influence extends beyond genetics13. Children raised in homes where drug use is normalised may develop maladaptive coping mechanisms, increasing their risk of later addiction. Early trauma, adverse childhood experiences (ACEs), and parental substance misuse further compound vulnerability. 

Q: Can someone be addicted to multiple drugs at the same time?

→ Yes, polysubstance use – where an individual is dependent on multiple substances simultaneously – is a well-documented phenomenon in addiction medicine.

A: Yes. The phenomena known as polysubstance addiction complicates treatment and increases health risks

Many individuals with substance use disorders engage in polydrug use14, either to enhance effects (eg., mixing opioids and benzodiazepines) or to counteract withdrawal symptoms. Research shows that a significant number of addicted individuals also misuse another substance15. 

This co-use can worsen cognitive impairment, increase overdose risk, and make withdrawal more severe. From a neurobiological perspective, different substances target overlapping but distinct pathways, leading to complex dependency patterns. 

Q: How can I spot the signs of drug addiction? 

→ Recognising addiction early is critical for intervention. Symptoms can manifest physically, psychologically, and behaviourally.

A: It varies, but look out for cognitive, emotional, & behavioural changes

Clinicians should look for persistent drug-seeking behaviours, loss of control over substance use, and withdrawal symptoms as key diagnostic markers (DSM-5 criteria for substance use disorder16). 

Physical signs may include weight loss, poor hygiene, and sleep disturbances, while psychological indicators often include anxiety, depression, and paranoia. Behavioural red flags can include social withdrawal, financial difficulties, and neglect of responsibilities. Notably, individuals may exhibit increased tolerance and escalating use over time. A comprehensive assessment – including patient history, screening tools (e.g., AUDIT, DAST), and family interviews – can help identify addiction early and guide appropriate treatment planning.

Final thoughts

Understanding the root causes of drug addiction is essential for clinicians seeking to provide effective, evidence-based care. It’s worth reaffirming: addiction is not simply a matter of willpower. It is a complex interplay of genetic predisposition, neurobiological changes, psychological distress, environmental stressors, and social determinants of health. 

Factors such as childhood trauma, mental health disorders, socioeconomic position, and exposure to high-risk environments all contribute to vulnerability; making a multidisciplinary, whole-person approach to treatment crucial.

As healthcare professionals, we must move beyond symptom management and focus on comprehensive, person-centered care. This includes early screening, trauma-informed interventions, behavioural therapy, and pharmacological support, as well as addressing family dynamics and social reintegration. By recognising addiction as a chronic yet treatable condition, clinicians can help reduce stigma, improve access to care, and empower patients on the road to recovery.

If you or someone you know is struggling with addiction, seeking timely professional support can make all the difference. Contact Harbor London today for personalised, discreet, expert-led addiction treatment and recovery solutions. 

References 

1. https://www.stir.ac.uk/news/2024/december-2024-news/campaign-to-end-stigma-around-drug-and-alcohol-deaths-receives-scottish-government-funding/
2. https://www.who.int/health-topics/drugs-psychoactive#:~:text=About%20296%20million%20people%20aged,drug%20use%20or%20drug%20dependence).
3. https://www.ons.gov.uk/peoplepopulationandcommunity/crimeandjustice/articles/drugmisuseinenglandandwales/yearendingmarch2024
4. https://www.mentalhealth.org.uk/explore-mental-health/statistics/substance-misuse-statistics
5. https://www.statista.com/statistics/1499700/illicit-drugs-use-by-type-in-the-uk/
6. https://commonslibrary.parliament.uk/research-briefings/cdp-2024-0050/
7. https://americanaddictioncenters.org/rehab-guide/addiction-genetic
8. https://www.yalemedicine.org/news/how-an-addicted-brain-works#:~:text=This%20happens%20because%20addictive%20substances,more%20than%20a%20natural%20reward.
9. https://pubmed.ncbi.nlm.nih.gov/9584965/
10. https://www.addictioncenter.com/community/these-are-the-5-most-addictive-substances-on-earth/
11. https://theconversation.com/the-five-most-addictive-substances-on-earth-and-what-they-do-to-your-brain-54862#:~:text=Heroin%20is%20an%20opiate%20that,dose%20required%20for%20a%20high.
12. https://www.sciencedirect.com/science/article/abs/pii/0376871694901546
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC3725219/
14. https://www.cdc.gov/stop-overdose/caring/polysubstance-use.html
15. https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2020.00569/full
16. https://pmc.ncbi.nlm.nih.gov/articles/PMC3767415/