Because gross pathology is not usually present, diagnosis of mental health problems, except for organic impairment, has to rely on a skilled professional like a psychiatrist or psychologist (see services below) who forms an opinion of the patient’s internal state of mind by means of an interaction or interview with the patient called the mental state examination. Like any doctor before the battery of lab tests that are now used became available, they will be looking out for unusual features in the person’s quality of appearance, behaviour and relationship.

To be more precise, they are looking for unusual features in the person’s:

• Appearance and behaviour: eg an unkempt appearance may indicate depression: unusual, bright clothes and makeup may indicate mania.
• Rapport: the degree to which the person is able to relate to the interviewer, and how this changes through the interview.
• Speech: whether it is slow, fast, easy, reluctant, comprehensible.
• Mood: elevated and euphoric, depressed, anxious, angry or irritable, labile (shifting rapidly), blunted (apparently emotionless), or incongruent (inappropriate to the situation).
• Thought: disorders of the stream of consciousness: sudden thoughts or blockages of thought which the person feels they have no control over: delusions: incoherency and unpredictability: repetitive and obsessive thoughts.
• Cognition: the general ability to form coherent thoughts and to comprehend.
• Perception: hallucinations, dizziness, distortions of time and space, ‘out of body’ feelings etc.
• Insight: self-awareness, including the awareness that something is wrong (if it is).

Reference is made to one of several diagnostic ‘bibles’ of psychology, of which the most often used is the Diagnostic and Statistical Manual (fourth edition) of the American Psychiatric Association.

This categorises mental illness and lists defining and distinguishing symptoms. Without attempting a comprehensive list, these are some of the more familiar and/or common conditions:

Adjustment disorder

Adjustment disorders are common and may happen to anyone. They are a period of mental turbulence the individual may go through after experiencing a sudden change or loss, such as bereavement, divorce, diagnosis with a serious illness (such as HIV), unemployment and so on. An adjustment disorder is diagnosed only if the person’s reaction to the change interferes markedly with their ability to lead their normal life. People may react with anxiety, depression, avoidant behaviour (social isolation) or a mix of all three.

Anxiety disorders

In anxiety disorders the normal emotion of fear has run out of control and disrupts the person’s life in some way. Anxiety disorders include agoraphobia and social phobia; the other specific phobias; stress disorder; panic attacks; and generalised anxiety disorder (a generalised state of jumpiness and fear about most situations). Anxiety has a large somatic component – as anyone who has had ‘nerves’ before an exam or presentation knows – and drug therapy often acts to calm down the physical symptoms of adrenaline overload such as pounding heart, cold sweats and hyperventilation so the person can function.

Two rather different and specific types of anxiety disorder are:

• Obsessive-compulsive disorder. In this the person finds themselves constantly ‘having to’ think or try not to think specific thoughts, or  to perform specific actions. Compulsive handwashing or having to check that the gas is not left on many times are examples, but probably more disabling are the internal circling thoughts or ‘ruminations’ that people with OCD force themselves to think. Sufferers may have the conviction that they will do something terrible like murder someone or blurt out obscenities unless they perform specific actions or think specific things. OCD can be quite disabling. What looks like agoraphobia can sometimes be OCD, as the person is unable to leave the house because the rituals required to do so are too elaborate. The millionaire Howard Hughes was a famous sufferer from the condition. OCD is not a particular risk factor for HIV as OCD sufferers tend to be hyper-careful about sexual health, though there are case reports of OCD being set off by HIV diagnosis. However one way OCD very commonly presents is as fear of disease and, in particular fear of AIDS. Many of the ‘worried well’ who consistently plague helplines and agencies with unlikely scenarios for having caught HIV in fact have OCD.
• Post-Traumatic Stress disorder. A unique diagnosis in that there has to be a specific precipitating event before it can be called PTSD. This is a particular state of anxiety brought on by having participated in or witnessed a traumatic event such as a natural disaster, accident, war and so on. It is characterised by the ‘Vietnam Vet’ picture of hair-trigger nerves, nightmares and flashbacks to the traumatic event. May also be produced by prolonged and repeated traumas such as childhood abuse, in which case it is often more difficult to treat. Traumatic events unsurprisingly are very stressful and may cause post-traumatic stress (PTS) in themselves; for PTS to be considered a disorder the stressed behaviour has to persist more than six months after the event and/or be brought on later by additional stressors that reawaken memories of the event. The core cause of PTSD is dissociation (see below under fight, flight or freeze).

Cognitive disorders

These are organic, neurological damage to the ability to think; drug-induced amnesia, fever-induced delirium and dementia are examples.

Dissociative disorders

In these the person avoids specific events or the stress of life by mentally or even physically absenting themselves. They include depersonalisation, where nothing feels real to the person or they don’t feel they are real (often part of a normal adjustment process such as grief or shock), fugue, where the person literally flees from their normal life, often with loss of memory, and dissociative identity disorder (DID), so-called ‘multiple personality disorder’, a rare but much-publicised condition in which the person compartmentalises their experience into different ‘sub personalities’ who may not be aware of each other’s experiences.

Eating disorders

Bulimia and anorexia. Among the most difficult of common disorders to treat.

Factitious disorders

In these the person makes up a physical or mental illness in order to gain attention or contact, usually repeatedly. Although the actual illness complained of is not present, the pattern of behaviour may disrupt life enough to be a mental illness in itself. Sometimes called Munchausen’s Syndrome when it applies to physical illnesses. Needless to say factitious disorders can be very difficult to distinguish from the real thing.

Impulsive disorders

An inability to control impulsive and often antisocial behaviour such as gambling addiction, kleptomania (compulsive stealing) or pyromania.

Mood disorders

The most common kind of mental illness, they may range in severity from mild depression (‘the blues’) to completely disabling mania or lifelong depression with psychotic (see below) delusions.

Divided into:

• Bipolar affective disorder (‘manic depression’) in which the person oscillates between mania (a heightened state of ‘speediness’ and euphoria which is distinguished from normal elevated mood by being socially maladaptive and out of touch with reality) to major depression.
• Unipolar illness in which the person relapses periodically from relative normality into sudden sharp periods of major depression.
• Dysthymia or minor depression. Has to last more than two years to be diagnosed. A general state of low mood, pessimism, and poor self esteem. Has been associated with sexual risk-taking; in one Australian study (Rogers) gay men with dysthymia were 2.36 times more likely than others to report unprotected sex with casual partners.

Major depressive disorder (MDD). This is distinguished from dysthymia by including more physical characteristics, and from unipolar depression by not being episodic. The person may feel and indeed be quite unable to get out of bed, care for themselves, etc, as well as suffering from crushing feelings of unworthiness, guilt and inadequacy. There is marked slowing of speech, concentration and memory without any obvious organic cause. Very high risk of suicide. Not associated with sexual risk because libido is also blunted.

Schizophrenia

About 1.1% of the world population has this condition. If there is a central characteristic of schizophrenia, it is boundary loss. A person with schizophrenia is unable to distinguish between their own thoughts and other people’s. They may attribute their own thoughts to alien messages or perceive that slogans on advertising hoardings are intended specifically for them. They may experience a general inability to keep thoughts under control, with streams of thought sliding rapidly into each other, and may adopt incomprehensible (to the outsider) rituals to attempt to assert some control over disordered thought processes. This may or may not be accompanied by hallucinations and organised delusions.

Schizophrenia is an example of a mental illness that used to be thought of as caused purely by upbringing and psychological factors and is now thought to be largely genetic and physiological in origin, with subtle changes apparent in the brain, especially of long term sufferers. Schizophrenics are rarely a danger to others (more often themselves) and the condition is treatable. Over a 30-year period, 25% of people who have had at least one episode completely recover, 35% will be much improved and relatively independent, 15% will be improved, but require extensive support, 10% will be hospitalized and unimproved and 15% will be dead (mostly from suicide). There is no evidence that people with HIV are more likely to have schizophrenia than average, but schizophrenics are more likely to have risk factors for HIV such as homelessness, survival sex and multiple partners, and 22% of men with schizophrenia in one survey (Cournos) had had sex with other men.

Sexual disorders

Divided into sexual dysfunction, sexual and gender identity disorders (transsexuality etc, or difficulty adjusting to it) and paraphilias or antisocial sexual behaviours such as exhibitionism, paedophilia, voyeurism, sexual sadism etc. Notoriously, homosexuality used to be included in this list until the APA removed it from DSM in 1973, ratifying this removal in 1975. However a person who is obsessed by fear of homosexuality or is deeply unhappy that they are gay may have a sexual identity disorder.

Somatoform disorders

Hypochondria or other preoccupation with illness, which may or may not actually produce physical symptoms. Differs from factitious illness in that the intention is not to deceive.

One very important point to note from DSM-IV is that as well as homosexuality, alcohol dependency and drug abuse are not in themselves seen as psychiatric disorders. Their use may indicate ‘self-medication’ for short-term crises or long-term personality disorders; people with narcissistic, antisocial or borderline disorders are particularly prone to addictions of this type. Equally, conditions ranging from schizophrenia (associated with cannabis and LSD), paranoia and anxiety (cocaine, methamphetamine and alcohol) depression (ecstasy and methamphetamine) and memory loss (alcohol) may be caused by prolonged drug use or even occasional use if the person is already unstable. However substance use in itself is not a diagnosis.