Classification and Patterns of Disease

Lessons

Senior 4 · Biology

Classification and Patterns of Disease

5 lessons

Lesson 4 of 5

Mental disorders and the effects of drug abuse

25 min

One in five, and one in twenty

In July and August 2018, interviewers from the Rwanda Biomedical Centre questioned 19 110 people aged 14 to 65 in every part of the country. About one woman in four and one man in six met the criteria for a mental disorder: 23.2 % of women and 16.6 % of men. Yet only 5.3 % of the people questioned had ever used a mental health service, although 61.7 % knew that such services existed.

Why would people who are ill not seek treatment that is available? Part of the answer is stigma: the shame attached to mental illness, and the old belief that it is a weakness, a curse or a punishment. Mental disorders are health conditions with causes, patterns and treatments, like any disease in this unit. This lesson also deals with drugs, because misuse of alcohol and other drugs is both a cause and a result of many mental disorders.

Definition

Mental health: "a state of mental well-being that enables people to cope with the stresses of life, realize their abilities, learn and work well, and contribute to their community" (World Health Organization).

Mental disorder: a condition with a clinically significant disturbance in a person's thinking, emotions or behaviour, usually causing distress or problems in daily life. Feeling sad after a loss is normal; a disorder lasts longer, is more severe and interferes with life.

Psychoactive drug: a substance that changes how the brain works, and so changes mood, perception or behaviour, for example alcohol, nicotine, cannabis and heroin. Drug abuse (misuse): use of a drug in a way, amount or situation that harms the user or others.

Tolerance: a need for a bigger dose to get the same effect. Withdrawal: unpleasant, sometimes dangerous symptoms when a regular user stops. Dependence (addiction): a state in which a person cannot control their use of a drug despite harm; it can be physical (withdrawal on stopping) or psychological (craving).

Common mental disorders

Disorder	Main features	Usual treatment
Depression (major depressive episode)	Low mood or loss of interest for at least two weeks, with poor sleep, tiredness, poor concentration, feelings of worthlessness, sometimes thoughts of death	Talking therapy, antidepressant medicines, social support
Anxiety disorders, including panic disorder	Persistent worry or sudden attacks of intense fear with a racing heart, breathlessness and sweating	Talking therapy (especially cognitive behavioural therapy), sometimes medicines
Post-traumatic stress disorder (PTSD)	After a terrifying event: reliving it in flashbacks or nightmares, avoiding reminders, being constantly on edge	Trauma-focused therapy, group and community support, sometimes medicines
Psychotic disorders such as schizophrenia	Losing touch with reality: hallucinations (hearing or seeing things others do not) and delusions (fixed false beliefs)	Antipsychotic medicines with psychological and social support
Bipolar disorder	Periods of depression alternating with periods of abnormally high mood and energy (mania)	Mood-stabilising medicines and therapy
Substance use disorders	Loss of control over alcohol or drug use, with tolerance, withdrawal and harm to health, study, work or family	Detoxification under medical care, counselling, rehabilitation, support groups

What causes mental disorders?

No single cause explains most mental disorders. Psychiatrists use a biopsychosocial model, in which risk builds up from three kinds of factor:

Biological: inherited alleles that raise risk (schizophrenia and bipolar disorder run in families), changes in brain chemistry, brain injury, infections such as cerebral malaria, and drugs and alcohol.
Psychological: trauma, especially in childhood; long-term stress; grief; ways of thinking that magnify problems.
Social: poverty, unemployment, violence, isolation, discrimination and the loss of family or community.

The Rwanda Mental Health Survey of 2018 shows how a shared trauma affects a population. Among survivors of the 1994 Genocide against the Tutsi who were interviewed, 35.0 % had a major depressive episode and 27.9 % had PTSD, compared with 12.0 % and 3.6 % in the general population. Mental health care, trauma counselling and community support for survivors are therefore part of Rwanda's public health work.

Disorder (Rwanda Mental Health Survey, 2018)	General population (19 110 people)	Genocide survivors (1 271 people)
Major depressive episode	12.0 %	35.0 %
Panic disorder	8.1 %	26.8 %
Post-traumatic stress disorder	3.6 %	27.9 %
Alcohol use disorder	1.6 % (men 3.4 %, women 0.3 %)	not given here
Ever used a mental health service	5.3 %	14.1 %

How psychoactive drugs act on the brain

Neurones pass signals across synapses using chemical transmitters. Psychoactive drugs change this signalling, and many of them increase the release of dopamine in the brain's reward pathway, the system that normally rewards eating and other survival behaviours. This is what makes drugs pleasurable, and what makes them habit-forming.

Group	Examples	Short-term effects	Long-term harm
Depressants: slow brain activity	Alcohol, sleeping pills, heroin and other opioids	Relaxation, slowed reactions, poor judgement, drowsiness; overdose stops breathing	Liver cirrhosis and cancers (alcohol), dependence, brain damage, violence and road crashes
Stimulants: speed brain activity	Nicotine, caffeine, cocaine, amphetamines, khat	Alertness, faster heart rate, raised blood pressure, less appetite	Tobacco: lung cancer, heart disease, stroke, chronic lung disease; cocaine: heart attack, psychosis
Cannabis	Marijuana, hashish	Altered perception and time sense, poor memory and coordination, anxiety	Dependence; in heavy teenage users, raised risk of psychosis and poorer memory and school results
Solvents (inhalants)	Glue, petrol fumes	Dizziness, confusion	Brain, liver and kidney damage; sudden death from heart failure

World Health Organization figures show the scale: alcohol caused about 2.6 million deaths worldwide in 2019, and tobacco kills more than 7 million people every year, including over 1.6 million non-smokers exposed to second-hand smoke.

Worked example 1: units of alcohol

Health services measure alcohol in units: one unit is 10 ml (8 g) of pure ethanol. The alcohol by volume (ABV) on a label is the percentage of the drink that is ethanol.

\text{units} = \frac{\text{volume of drink in ml} \times \text{ABV}}{1000}

A man drinks three 500 ml bottles of beer at 5.0 % ABV and one 50 ml glass of spirit at 40 % ABV in an evening. How many units has he drunk?

One beer: $\frac{500 \times 5.0}{1000} = 2.5$ units, so three beers: $3 \times 2.5 = 7.5$ units.
Spirit: $\frac{50 \times 40}{1000} = 2.0$ units.
Total: $7.5 + 2.0 = 9.5$ units in one evening. Drinking a large amount in one session (heavy episodic drinking) is the pattern WHO links to most alcohol harm: injuries, violence and alcohol poisoning.

Worked example 2: why a regular drinker needs more

Explain, in terms of synapses, why a person who drinks heavily every day (a) needs more alcohol to feel the same effect and (b) may shake, sweat and even have fits if they suddenly stop.

(a) Alcohol increases the effect of GABA, the brain's main inhibitory transmitter. With constant alcohol, neurones adapt: they reduce the number or sensitivity of GABA receptors and increase excitatory signalling, to keep activity near normal. Now a bigger dose is needed to produce the same depressant effect: tolerance.
(b) When alcohol is suddenly removed, the adapted brain is left with too little inhibition and too much excitation. Over-activity shows as shaking, sweating, anxiety, a racing heart and, in severe cases, seizures: withdrawal. This is why stopping after long heavy use should be done under medical care.

TED-Ed: "What causes addiction, and why is it so hard to treat?" (Judy Grisel). Watch for how the brain adapts to repeated drug use, producing tolerance, withdrawal and craving.

Warning

Safety and common mistakes

Never mix alcohol with other depressants such as sleeping pills or opioids: together they can stop breathing. Never drive or ride after drinking.
Saying that mental illness is a weakness or a curse. It is a health condition, and it can be treated.
Thinking cannabis is harmless because it is "natural". Tobacco and many poisons are natural too; cannabis can cause dependence and psychosis.
Confusing tolerance with dependence. Tolerance is needing a bigger dose; dependence is being unable to stop.
Growing, selling or using narcotic drugs such as cannabis or heroin is a crime in Rwanda. Drug dealing can be reported to the Rwanda Investigation Bureau on 166, and abuse of a child on 116. If you or a friend are struggling with low mood, fear or drugs, talk to a parent, teacher, school nurse or health centre: asking for help is the first step of treatment.

Tip

Memory hook. The three faces of a drug habit: Tolerance (needs Too much), Withdrawal (Worse without it), Dependence (Doesn't stop despite harm). For the causes of mental disorders, think B-P-S: Body, Personal history, Society.

✦

Practice: mental disorders and drug abuse

Distinguish between normal sadness and a major depressive episode.
Give one biological, one psychological and one social risk factor for depression.
Explain why PTSD was far more common among survivors of the 1994 Genocide against the Tutsi than in the general population in the 2018 survey.
A 330 ml bottle of beer is 6.0 % ABV. Calculate the number of units in four bottles.
Cocaine blocks the reuptake of dopamine. Explain how this produces a "high", and suggest why the user feels low when the drug wears off.
A doctor records smoking in pack-years: $\text{pack-years} = \frac{\text{cigarettes per day}}{20} \times \text{years of smoking}$ . Calculate the pack-years of a man who smoked 30 cigarettes a day for 12 years.
Suggest two reasons why only 5.3 % of people in the 2018 survey had used mental health services, and one way to raise this figure.

Show answersHide answers

Sadness after a loss or disappointment is a normal reaction; it eases with time and does not stop daily life. A major depressive episode lasts at least two weeks, with low mood or loss of interest most of the day, plus symptoms such as poor sleep, tiredness, poor concentration and worthlessness, and it interferes with study, work or relationships.
Biological: a family history (inherited risk), or chronic illness. Psychological: trauma or long-term stress. Social: poverty, isolation, violence or loss of a family member.
Survivors lived through extreme, prolonged trauma: violence, the murder of family members, and the loss of homes and communities. PTSD is caused by exposure to such events, and the survivors also faced continuing grief and social and economic hardship, which keep symptoms going.
One bottle: $\frac{330 \times 6.0}{1000} = 1.98$ units; four bottles: $4 \times 1.98 = 7.92 \approx 7.9$ units.
Normally dopamine is taken back into the first neurone, ending the signal. Blocking reuptake leaves dopamine in the cleft, so reward receptors are stimulated strongly and for longer: euphoria. With repeated use, receptors are reduced and natural dopamine is less effective, so when the drug wears off the reward system is under-stimulated: low mood and craving.
$\frac{30}{20} \times 12 = 18$ pack-years.
Reasons: stigma and fear of being labelled; not recognising the symptoms as an illness; belief in other causes; cost or distance to services. To raise use: public awareness campaigns, training community health workers and teachers to recognise disorders and refer people, and offering mental health care at nearby health centres.

Quick check

Match each term to its meaning.

Tap one on the left, then its partner on the right.

Key points

Mental disorders (depression, anxiety, PTSD, psychosis, bipolar disorder, substance use disorders) are health conditions with biological, psychological and social causes, and they can be treated.
Rwanda's 2018 survey found a mental disorder in 23.2 % of women and 16.6 % of men, much higher rates among survivors of the 1994 Genocide against the Tutsi, and very low use of services (5.3 %).
Psychoactive drugs act at synapses: depressants boost GABA, stimulants raise dopamine or mimic transmitters. Repeated use causes tolerance, withdrawal and dependence.
Units of alcohol = volume (ml) × ABV ÷ 1000. Alcohol and tobacco together cause millions of deaths a year worldwide.

Sources and credits

4.5: Substance Use and Abuse and 15.2: What Are Psychological Disorders?, from Psychology 2e by OpenStax (Rose M. Spielman, William J. Jenkins, Marilyn D. Lovett and others), via LibreTexts Social Sciences, licensed under CC BY 4.0. Used for psychological disorders, drug groups, tolerance, withdrawal and dependence. Adapted by Ganzaa.
Data: Y. Kayiteshonga, V. Sezibera and others, "Prevalence of mental disorders, associated co-morbidities, health care knowledge and service utilization in Rwanda", BMC Public Health (2022), CC BY 4.0, reporting the Rwanda Mental Health Survey 2018; World Health Organization fact sheets Mental health (11 September 2026), Alcohol (28 June 2024) and Tobacco and nicotine (26 June 2026); hotlines from the Rwanda Investigation Bureau contact page.
Figure 1, the tables, worked examples, practice and quick check: written by Ganzaa.
Photo: Dedios Nsabimana, CC BY-SA 4.0, via Wikimedia Commons.
Video: "What causes addiction, and why is it so hard to treat?", Judy Grisel, TED-Ed, embedded from YouTube.

1One in five, and one in twenty

2Common mental disorders

3What causes mental disorders?

4How psychoactive drugs act on the brain

One in five, and one in twenty

Common mental disorders

What causes mental disorders?

How psychoactive drugs act on the brain