Classification of Diseases

Lessons

Senior 1 · Biology

Classification of Diseases

5 lessons

Lesson 4 of 5

Physical and mental disorders

25 min

Two classmates

Habimana has epilepsy. About twice a year he has a seizure; the rest of the time he takes his tablets and is one of the best students in mathematics. Umutoni has felt low and tired for months; she has stopped playing netball and hardly talks at break. Some classmates whisper that Habimana is "cursed" and that Umutoni is "just lazy". Both are wrong. Each has a health condition that can be understood, treated and supported, and neither can be caught from them.

Definition

Disorder: a condition in which a part of the body or mind does not work in the usual way.

Physical disorder: a disorder that affects the structure or working of the body. Examples: epilepsy, asthma, a hearing impairment.

Mental disorder (mental illness): a disorder that affects a person's thinking, feelings or behaviour enough to disturb their daily life for a long time. Examples: depression, anxiety disorders, post-traumatic stress disorder (PTSD).

Stigma: negative beliefs and unfair treatment directed at people because of a condition they have.

Physical and mental disorders compared

Feature	Physical disorders	Mental disorders
What is affected	the structure or working of an organ or body system	thinking, mood, feelings and behaviour
Examples	epilepsy, asthma, visual or hearing impairment, cleft lip, paralysis after an injury	depression, anxiety disorders, PTSD, psychosis, drug or alcohol dependence
Possible causes	genes, injury, infection, a problem before birth, sometimes unknown	genes and brain chemistry, stress, loss, violence or trauma, drug use; usually several together
What helps	medicines, surgery, aids (glasses, hearing aids, wheelchairs), therapy	talking therapies (counselling), medicines, support from family and friends

Neither kind is a punishment, a curse or a sign of weakness, and neither can be caught by being near someone. Physical and mental health are also linked: a long illness can lead to depression, and depression can cause headaches, tiredness and poor sleep.

Mental health is a continuum

Figure 1: Mental health changes over time, like physical health. Noticing the signs early and talking to someone helps a person move back towards the healthy end.

Everyone has mental health, just as everyone has physical health, and everyone moves along this bar. After an exam failure or the loss of someone you love, it is normal to feel sad or worried for a while. It becomes a disorder when the distress is strong, lasts for weeks and stops a person coping with daily life.

Mental health in Rwanda

In 2018 the Rwanda Biomedical Centre (RBC) surveyed more than 19,000 people aged 14 to 65. About one in five (20.5%) had at least one mental disorder; the most common were major depressive episodes (depression, 12.0%), panic disorder (8.1%) and PTSD (3.6%). Among survivors of the 1994 Genocide against the Tutsi, major depressive episodes (35.0%) and PTSD (27.9%) were far more common. Most people (61.7%) knew that mental health services existed, but only 5.3% had ever used them. Mental health care has been brought from the national referral hospitals down to district hospitals and health centres, where trained nurses and other health workers assess and treat people.

Worked example 1: interpreting the survey

Using the 2018 figures, imagine a group of 1,000 people aged 14 to 65. (a) About how many would have a mental disorder? (b) How many would know about services, and how many would have used them? (c) What does the difference suggest?

(a) $\frac{20.5}{100} \times 1\,000 = 205$ people.
(b) Knew about services: $\frac{61.7}{100} \times 1\,000 = 617$ . Had used them: $\frac{5.3}{100} \times 1\,000 = 53$ .
(c) About 205 people might need help, and most know it exists, yet only about 53 have used it. Fear of being judged (stigma), not recognising the signs, and distance or cost can keep people away.

Conclusion: mental disorders are common, and reducing stigma is one of the most useful things a school can do.

Worked example 2: classifying conditions in two ways

Classify each condition as physical or mental, and as infectious or non-infectious: (a) depression; (b) epilepsy; (c) paralysis of a leg caused by polio.

(a) Depression affects mood and thinking: mental. It is not caused by a pathogen: non-infectious.
(b) Epilepsy is caused by bursts of abnormal electrical activity in the brain: a physical disorder of the nervous system. It cannot be caught: non-infectious.
(c) Polio paralysis is a physical disability. It was caused by the polio virus, an infectious disease, although the paralysis itself cannot be passed on. Vaccination prevents it.

Lesson: the two classifications answer different questions (which part is affected? and can it spread?), so a condition needs both.

Warning

Respect and safety. Use person-first words: say "a person with epilepsy", not "an epileptic"; "a student with depression", not "a mad person". Never laugh at or exclude someone because of a disorder. First aid for a seizure (see the primary survey in Unit 1): move hard objects away, cushion the head, and time the seizure; do not hold the person down or put anything in their mouth; when the jerking stops, turn them onto their side and stay with them. Call for help if the seizure lasts more than five minutes, another seizure follows, the person is injured, has trouble breathing or does not wake up afterwards, or it is their first seizure. If you or a friend feel unable to cope or have thoughts of self-harm, tell a trusted adult, a teacher, a community health worker or the health centre straight away.

We All Have Mental Health (Anna Freud National Centre for Children and Families). An animation made for schools: watch for how mental health can move up and down, and for the simple ways to look after it and to ask for help.

Tip

Memory hook: "Body or mind? Caught or not?" Classify any condition twice: physical or mental, then infectious or non-infectious. And remember the three T's for a friend who is struggling: Talk, Tell a trusted adult, Time together.

✦

Practice: physical and mental disorders

Define a physical disorder and a mental disorder, with one example of each.
Give two possible causes of a mental disorder.
What is stigma? Give one example of stigma and one way to reduce it.
State three things you should do, and two things you should not do, when someone has a seizure.
Explain why feeling sad for a few days after a loss is not necessarily a mental disorder.
In the 2018 survey, 12.0% had a major depressive episode. About how many people is that in a group of 500?
Rewrite in respectful, person-first language: "The epileptic boy and the crazy girl sat together."
A classmate says, "Mental illness is just weakness; he should pull himself together." Evaluate this statement.

Show answersHide answers

A physical disorder affects the structure or working of the body (for example epilepsy or asthma). A mental disorder affects thinking, feelings or behaviour enough to disturb daily life for a long time (for example depression or an anxiety disorder).
Any two: genes and brain chemistry; stress; loss; violence or trauma; drug or alcohol use.
Negative beliefs and unfair treatment because of a condition, such as calling someone "cursed" or refusing to sit with them. It can be reduced by learning the facts, using respectful language and including people.
Do: move hard objects away, cushion the head, time the seizure, turn the person onto their side afterwards, stay with them, get help if it lasts over five minutes. Do not: hold them down or put anything in their mouth.
Sadness after a loss is a normal reaction. It becomes a disorder only when strong distress lasts for weeks and stops the person coping with daily life.
$\frac{12.0}{100} \times 500 = 60$ people.
For example: "The boy with epilepsy and the girl with a mental illness sat together."
It is wrong. Mental disorders have real causes (genes, brain chemistry, stress, trauma) and are health conditions, not a choice or a weakness. People recover with treatment and support; blaming them adds stigma and stops them seeking help.

Key points

Physical disorders affect the body's structure or working; mental disorders affect thinking, feelings and behaviour.
Both have real causes, can be treated or supported, and cannot be caught; stigma makes them worse.
Mental health is a continuum; noticing signs early and talking to someone helps.
In Rwanda's 2018 survey, about one in five people aged 14 to 65 had a mental disorder, but few had used services.

Sources and credits

Rwanda Mental Health Survey 2018: Yvonne Kayiteshonga and others, "Prevalence of mental disorders, associated co-morbidities, health care knowledge and service utilization in Rwanda", BMC Public Health 22, 1858 (2022), licensed under CC BY 4.0. Figures quoted, not adapted.
15.1: Characteristics of Infectious Diseases, from Microbiology (OpenStax), via LibreTexts Biology, licensed under CC BY 4.0.
Video: We All Have Mental Health, Anna Freud National Centre for Children and Families, embedded from YouTube.

Written by Ganzaa: the classroom case, Figure 1, the table, the worked examples, the first-aid guidance and the practice questions.

1Two classmates

2Physical and mental disorders compared

3Mental health is a continuum

4Mental health in Rwanda

Two classmates

Physical and mental disorders compared

Mental health is a continuum

Mental health in Rwanda