Organic Mental Syndromes (Organic Causes of Psychiatric Symptoms)

Organic Mental Syndromes

(Organic Causes of Psychiatric Symptoms) 


The term ‘organic mental disorder/syndrome’ in psychiatry is used when there is a ‘disease of the body’ which present with psychiatric symptoms. In contrast, ‘functional mental disorders’ are considered to be ‘disease of the mind’. Classifying psychiatric disorders in this way is becoming outdated now that more is known about the ‘organic’ basis of functional illnesses, such as abnormal brain structure in schizophrenia. However, the term organic is still commonly used in clinical practice and communication and is included in the ICD 10.

Patients with organic disease can present with psychiatric symptoms. There are several ways this may occur,

1. Psychiatric symptoms of organic disorders:

Table 1 shows some of the organic illnesses, in which psychiatric symptoms occur as a direct result of the organic disease process.







-Most dementias (especially vascular and Huntington’s)    -Parkinson’s disease  -Multiple sclerosis                   -Neurosyphilis

-Hypothyroidism        -Cushing’s syndrome -Hypopituitarism                                 -hyperparathyroidism -Addison’s disease

-Anaemia                 -infections                 -Carcinomatosis     -Prophyria

-Corticosteroids       -?-blockers                -calcium channel blockers                    -L-dopa                    – OCP

Elation or Hypomania /Mania

-Multiple sclerosis   -Neurosyphilis         -TLE

-Cushing’s syndrome

-Carcinoma            -CNS infections

-Corticosteroids        -Antidepressants


-Parkinson’s disease -CVA                       -Brain injury

-Hyperthyroidism       -Hypoglycemia           -Phaechromocytoma

-Anaemia               –

-SSRI Antidepressants        -Anticonvulsants


-Huntington’s disease                      -Multiple sclerosis   – Space occupying lesion                        -CNS infection

-Hyperthyroidism          -Cushing’s disease

-SLE                      -Acute prophyria

-Corticosteroids       -?-blockers               -L-dopa                        -Sympathomimetics

ICD 10 classifies such episodes as ‘other mental disorders due to brain damage and dysfunction and physical disease’. By ‘other mental disorders’, it means disorders other than dementia, amnesic syndrome and delirium which are also due to brain damage and dysfunction or physical diseases. It splits theses other mental disorders into subgroups, depending on the nature of the psychiatric symptoms caused by the organic disorder. Examples of these include:

  • Organic hallucinosis
  • Organic delusional disorder
  • Organic mood disorder
  • Organic anxiety disorder

In term of assessment, the possibility of an organic cause should always be kept in mind when assessing patients with psychiatric symptoms. There may be clues that patient has an organic disorder, some factors which suggest an organic cause of psychiatric symptoms are:

  • Ø Failure to respond to treatment
  • Ø Different to previous psychiatric presentations
  • Ø Abnormal physical examination
  • Ø No clear aetiology
  • Ø Other symptoms of organic illness
  • Ø Atypical psychiatric presentation

As an example, think of differential diagnosis of a patient with anxiety an breathlessness. These symptoms are often caused by panic disorder. However, it would be important to look for symptoms and signs of organic disorders known to cause anxiety. For instance, the patient might also show evidence of heart intolerance and brisk deep tendon reflexes, in which case hyperthyroidism should be considered. For instance, if their anxiety was mild and seemed to be secondary to their breathlessness, a cardiac or respiratory cause should be considered.

An unusual presentation should also lead one to suspect a medical cause. For instance, first onset panic disorder would be very unusual in a 50-year-old man with no previous psychiatric history and no recent stresses or adverse life events. With such a presentation, organic causes should be vigorously investigated (not just the routine).

Recognition of medical disorders presenting in this way is clearly important as the patient will not usually recover until the underlying cause has been treated. Symptomatic treatment with psychotropic drugs may be required before the medical disorder has been treated. They also may be needed if the medical condition is untreatable (e.g. carcinoma), or if psychiatric symptoms persist after successful treatment of the medical condition (e.g. epilepsy). 

2. Psychiatric illness occurring as an indirect result of organic illness:

Medical illness is often distressing. It is not surprising therefore that psychiatric illness often occurs as a result. The consequences of medical illness most likely to cause this are shown in figure 1.

Patient at risk of psychiatric illness, such as those with a family history or past psychiatric history, are more likely to develop a psychiatric illness when medically ill, just as they are more likely to when faced with adverse life event (bio-psycho-social interaction in causation).  It is important to remember that medical illnesses will have different consequences for different patients. For example, MI in a heavy goods vehicle driver will leave them unable to return to their previous job, raising the risk of depression. A stomach inflammation in a patient whose father died of gastric cancer might present with hypochondriasis or panic attacks.

Once a psychiatric illness has developed, it can often exacerbate symptoms of the physical illness which precipitated it. For instance, depression often results in an exacerbation of pain. Patients’ general level of function, which is often reduced as a result of their medical illness, may be reduced further as a result of psychiatric symptoms such as lethargy, anxiety or loss of confidence.

The risk of psychiatric consequences of medical illness are reduced by giving patients a full explanation of the illness and what can be done to help them, paying particular attention to any specific fears the patient may have. Practical advice about how they can cope with the illness is also useful. Involving patients’ families in this process will clarify the support they need to give the patient and allow them to voice concerns of their own. All this is best carried out by members of the medical team (rather than a referral to a mental health worker) dealing with the patient and assigning in some specialist services, such as diabetic clinics, a member of staff designated to carry out this.

In addition to the general measures, specific treatments for the psychiatric disorders will be required in some cases. Standard treatment should be used, provided they are not contra-indicated by the medical illness. This is most likely to be the case for drug treatments and a list of medical conditions which can be exacerbated by the psychotropic drugs is given below. The list includes only few medications and the focus is their antimuscarinic effect:

  • Cardiovascular disease.
  • Glaucoma
  • Constipation
  • Prostatism
  • Dementia

It is also important to be aware of the potential drug interactions in patients receiving treatment for physical and psychiatric illness (e.g. fatal in some cases, as in patient with lithium and some diuretics)  

3. Organic and psychiatric illness occurring together by chance:

Organic and psychiatric illness are both common and so it is not surprising that they both often occur together by chance. When they do occur together ,each can make the other worse. The physical and psychiatric conditions should be treated in the usual way, bearing in mind the side effects and the interactions of both.

4. Psychiatric side-effects of medication

As mentioned above and with the example of the antimuscarinic side effect with many of the psychotropic medications. If such side effects occur the dose should be reduced or an alternative drug should be used. Occasionally, the risk of doing this outweighs the benefit and in such cases the psychiatric symptoms may require separate treatment.


1. Stevens L, Rodin I, Psychiatry: An illustrated colour text, Churchill Livingstone 2001

2. Steple D. Oxford Handbook of Psychiatry, Oxford University Press, 2006

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