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Psychosis is a psychiatric classification for a mental state in which
the perception of reality is distorted. Persons experiencing a psychotic
episode may experience hallucinations (often auditory or visual
hallucinations), hold paranoid or delusional beliefs, experience
personality changes and exhibit disorganized thinking (see thought
disorder). This is sometimes accompanied by a lack of insight into the
unusual or bizarre nature of their behaviour and an inability to cope in
Psychosis is usually considered by mainstream psychiatry to be a symptom
of severe mental illness, such as schizophrenia or bipolar disorder
(manic depression). It may also occur in severe cases of depression,
brain injury or drug overdose. Chronic psychological stress cultures
psychotic states, however the exact neurological mechanism is uncertain.
Psychosis triggered by stress in the absence of any other mental illness
is known as brief reactive psychosis. The direct effects of
hallucinogenic drugs are not usually classified as psychosis, as long as
they abate when the drug is metabolised from the body.
Psychosis is a descriptive term for a complex group of behaviours and
experiences and as such is not a medical explanation in itself. Perhaps
because of this, it is often confused with syndromes which may seem
similar on the surface, or with words which may suggest, or seem to
suggest a likeness.
The term psychosis should be distinguished from the concept of insanity,
which is a legal term denoting that a person should not be criminally
responsible for his actions. Similarly, it should be distinguished from
psychopathy, a personality disorder often associated with violence, lack
of empathy and socially manipulative behaviour. Despite the fact that
both are colloquially abbreviated to 'psycho', psychosis bears little
similarity to psychopathy's core features, particularly with regard to
violence, which rarely occurs in psychosis, and the distortion of
perceived reality, which rarely occurs in psychopathy.
It should also be distinguished from the state of delirium, in that a
psychotic individual may be able to perform actions that require a high
level of intellectual effort in clear consciousness. Finally, it should
be distinguished from mental illness. Psychosis may be regarded as a
symptom of other mental illnesses, but as a descriptive concept it is
not considered an illness in its own right. For example, persons with
schizophrenia can have long periods without psychosis and persons with
bipolar disorder and depression can have mood symptoms without
psychosis. Conversely, psychosis can occur in persons without chronic
mental illness as a result of an adverse drug reaction or extreme
Psychosis has been of particular interest to critics of mainstream
psychiatric practice who argue that it may simply be another way of
constructing reality and is not necessarily a sign of illness. For
example, R. D. Laing has argued that psychosis is a symbolic way of
expressing concerns in situations where such views may be unwelcome or
uncomfortable to the recipients. Thomas Szasz has focused on the social
implications of labelling people as psychotic, a label which he argues
unjustly medicalises different views of reality so such unorthodox
people can be controlled by society.
Etymology: The word psychosis was first used by Ernst von Feuchtersleben
in 1845 as an alternative to insanity and mania and stems from the Greek
psykhe (mind) and osis (diseased or abnormal condition). The word was
used to distinguish disorders which were thought to be disorders of the
mind, as opposed to neurosis, which was thought to stem from a disorder
of the nerves.
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A psychotic episode can be significantly coloured by mood. For example,
people experiencing a psychotic episode in the context of depression may
experience persecutory or self-blaming delusions or hallucinations,
whilst people experiencing a psychotic episode in the context of mania
may form grandiose delusions or have an experience of deep religious
Although usually distressing and regarded as an illness process, some
people who experience psychosis find beneficial aspects and value the
experience or revelations that stem from it.
Hallucinations in psychosis
Hallucinations are defined as sensory perception in the absence of
external stimuli. Psychotic hallucinations may occur in any of the five
senses and take on almost any form, which may include simple sensations
(such as lights, colours, tastes, smells) to more meaningful experiences
such as seeing and interacting with fully formed animals and people,
hearing voices and complex tactile sensations.
Auditory hallucinations, particularly the experience of hearing voices,
is a common and often prominent feature of psychosis. Hallucinated
voices may talk about, or to the person, and may involve several
speakers with distinct personas. Auditory hallucinations tend to be
particularly distressing when they are derogatory, commanding or
Delusions and paranoia
Psychosis may involve delusional or paranoid beliefs. Karl Jaspers
classified psychotic delusions into primary and secondary types. Primary
delusions are defined as arising out-of-the-blue and not being
comprehensible in terms of normal mental processes, whereas secondary
delusions may be understood as being influenced by the person's
background or current situation.
Thought disorder describes an underlying disturbance to conscious
thought and is classified largely by its effects on speech and writing.
Affected persons may show pressure of speech (speaking incessantly and
quickly), derailment or flight of ideas (switching topic mid-sentence or
inappropriately), thought blocking, rhyming or punning.
Lack of insight
One important and puzzling feature of psychosis is usually an
accompanying lack of insight into the unusual, strange or bizarre nature
of the person's experience or behaviour. Even in the case of an acute
psychosis, the sufferer may seem completely unaware that their vivid
hallucinations and impossible delusions are in any way unrealistic. This
is not an absolute, however; insight can vary between individuals and
throughout the duration of the psychotic episode.
In some cases, particularly with auditory and visual hallucinations, the
patient has good insight and this makes the psychotic experience even
more terrifying in that the patient realizes that he should not be
seeing demons and angels or hearing voices, but does.
Medical understanding of psychosis
There are a number of possible causes for psychosis. Psychosis may be
the result of an underlying mental illness such as Bipolar disorder
(also known as manic depression), and schizophrenia. Psychosis may also
be triggered or exacerbated by severe mental stress and high doses or
chronic use of drugs such as amphetamines, LSD, PCP, cocaine or
scopolamine. However, incidence of psychosis resulting from a single
administration of any drug is rare, although cases have been reported in
the medical literature suggesting a person's sensitivities to new
compounds can be unpredictable. As can been seen from the wide variety
of illness and conditions in which psychosis has been reported to arise
(including for example, AIDS, leprosy, malaria and even mumps) there is
no singular cause of a psychotic episode.
The division of the major psychoses into manic depression and dementia
praecox (later renamed to schizophrenia) was made by Emil Kraepelin, who
attempted to create a synthesis of the various mental disorders
identified by 19th century psychiatrists, by grouping diseases together
based on classification of common symptoms. Kraeplin used the term
'manic depression' to describe the whole spectrum of mood disorders, in
a far wider sense than it is usually used today. In Krapelin's
classification this would include 'unipolar' clinical depression, as
well as bipolar disorder and other mood disorders such as cyclothymia.
These are characterised by problems with mood control and the psychotic
episodes appear associated with disturbances in mood, and patients will
often have periods of normal functioning between psychotic episodes even
without medication. Schizophrenia is characterized by psychotic episodes
which appear to be unrelated to disturbances in mood, and most
non-medicated patients will show signs of disturbance between psychotic
Psychotic episodes may vary in duration between individuals. In brief
reactive psychosis, the psychotic episode is related directly to a
specific stressful life event so patients may spontaneously recover
normal functioning within two weeks. Patients who are undergoing brief
reactive psychosis due to drugs or stress generally appear with the same
symptoms as a person who is psychotic as a result of a mental illness,
and this fact has been used to support the notion that mental illness
has a biological basis.
Psychosis and brain function
The first brain image of person with psychosis was completed as far back
as 1935 using a technique called pneumoencephalography1 (a painful and
now obsolete procedure where cerebrospinal fluid is drained from around
the brain and replaced with air to allow the structure of the brain to
show up more clearly on an X-ray picture).
Pneumoencephalogram of person with psychosis, 1935Modern brain imaging
studies, investigating both changes in brain structure and changes in
brain function of people undergoing psychotic episodes have shown mixed
A 2003 study investigating structural changes in the brains of people
with psychosis showed there was significant grey matter reduction in the
cortex of people before and after they became psychotic2. Findings such
as these have led to debate about whether psychosis is itself neurotoxic
and whether potentially damaging changes to the brain are related to the
length of psychotic episode. Recent research has suggested that this is
not the case3 although further investigation is still ongoing.
Functional brain scans have revealed that the areas of the brain that
reacts to sensory perceptions are active during psychosis. For example,
a PET or fMRI scan of a person who claims to be hearing voices may show
activation in the auditory cortex, or parts of the brain involved in the
perception and understanding of speech.
On the other hand, there is not a clear enough psychological definition
of belief to make a comparison between different people particularly
valid. Brain imaging studies on delusions have typically relied on
correlations brain activation patterns with the presence of delusional
One clear finding is that persons with a tendency to have psychotic
experiences seem to show increased activation in the right hemisphere of
the brain4. This increased level of right hemisphere activation has also
been found in healthy people who have high levels of paranormal beliefs5
or in people who report mystical experiences6. It also seems to be the
case that people who are more creative are also more likely to show a
similar pattern of brain activation7. Some researchers have been quick
point out that this in no way suggests that paranormal, mystical or
creative experiences are in any way by themselves a symptom of mental
illness, as it is still not clear what makes some such experiences
beneficial whilst others lead to the impairment or distress of
diagnosable mental pathology. However, people who have profoundly
different experiences of reality or hold unusual views or opinions have
traditonally held a complex role in society, with some being viewed as
kooks, whilst others are lauded as prophets or visionaries.
Psychosis has been traditionally linked to the neurotransmitter
dopamine, particularly an excess of dopamine in the limbic system (a
structure deep within the brain). The development of effective
antipsychotic medication played a large part in the success of this
view, as the first effective antipsychotic drugs were dopamine blockers.
In addition, drugs that increase the concentration of dopamine tend to
trigger psychotic episodes.
Nevertheless, the connection between dopamine and psychosis is generally
believed to be complex. First of all, while anti-psychotic drugs
immediately block dopamine receptors, they usually take a week or two to
reduce the symptoms of psychosis. Moreover, newer and equally as
effective antipsychotic drugs actually block slightly less dopamine in
the brain than older drugs whilst also affecting serotonin levels,
suggesting the 'dopamine hypothesis' is vastly oversimplified.
Psychiatrist David Healy has criticised pharmaceutical companies for
promoting particular scientific theories that favour their medication
and encouraging a purely biological account of mental illness8, whilst
ignoring social and developmental factors which are known to be
important influences in the aetiology of psychosis. See the article on
the dopamine hypothesis of psychosis for further discussion of this
Some theories regard many psychotic symptoms to be a problem with the
perception of ownership of internally generated thoughts and
experiences9. For example, the experience of hearing voices may arise
from internally generated speech that is mislabelled by the psychotic
person as coming from an external source.
It has also been argued that psychosis exists on a continuum as
everybody may have some unusual and potentially reality-distorting
experiences in their life. This has been backed up by research showing
that experiences such as hallucinations have been experienced by large
numbers of the population who may never be impaired or even distressed
by their experiences10. In this view, people who are diagnosed with a
psychotic illness may simply be one end of a spectrum where the
experiences become particularly intense or distressing (see schizotypy).
Cannabis and psychosis
There is now growing evidence for a small but significant link between
cannabis use and vulnerability to psychosis11. Some studies indicate
that cannabis use correlates with a slight increase in psychotic
experience, which may trigger full-blown psychosis in some people. Early
studies have been criticized for failing to consider other drugs (such
as LSD) that the subjects may also have used before or during the study,
as well as other factors such as possible pre-existing mental health
issues. However, more recent studies with better control have still
found a small increase in risk for psychosis in cannabis users. It is
still not clear whether this is a causal link, and it may be that
cannabis use only increases the chance of psychosis in people already
predisposed to it. The fact that cannabis use has increased over the
past few decades, whereas the rate of psychosis has not, suggests that a
direct causal link is unlikely for all users.
Non-psychiatric conditions and psychosis
Psychosis can be a feature of several diseases, often when the brain or
nervous system is directly affected. However, the fact that psychosis
can occasionally arise in parallel with number of ailments (including
diseases such as flu or mumps for example) suggests that a variety of
nervous system stressors can lead to a psychotic reaction. Psychosis
arising from non-psychiatric conditions is sometimes known as 'secondary
psychosis'. The mechanisms by which this happens is still not clear, but
the non-specificity of psychosis has led Tsuang and colleagues to argue
that "psychosis is the 'fever' of mental illness - a serious but
There are some non-psychiatric conditions which are linked particularly
to psychosis, which may include:
- Systemic Lupus Erythematosus (it is one of the 19 types of nervous
system involvement in SLE).
- Brain tumours
- dementia with Lewy bodies
- Multiple sclerosis