What could be the reasons that lead to the change in nervous system function described on the previous page?

The answer seems to be that there are many potential reasons why an individual can become vulnerable to functional symptoms. These reasons can be divided up in to

Predisposing Factors: things that happened before the symptoms started

Precipitating Factors: things that happened at the time the symptoms started

Perpetuating Factors: things that happened after the symptoms started

These factors can be

Biological: for example there probably is a genetic vulnerability to these symptoms;

Psychological: for example when you worry that a headache might be due to a brain tumour it tends to make the headache worse and

Social: for example, if you don't enjoy your job and your boss is mean to you , you will tend to feel worse.

This is called the "biopsyschosocial model of illness". It doesn't just apply to functional symptoms. All illness has a psychological and social dimension. Someone with multiple sclerosis who feels miserable or has a lot of debt will tend to experience worse symptoms than someone with multiple sclerosis who is not unhappy and has no other life stresses.

Our models of why people get functional symptoms are incomplete. Many of the factors that seem to be relevant are also relevant for lots of other symptoms.

Its still often unclear why someone with these vulnerabilities should for example, become weak down one side, or start to develop a tremor.

I have explained some ideas about why these individual symptoms might happen on the relevant pages (see weakness, sensory symptoms, seizures, movement disorder)

The table below shows some factors which can be relevant in the development of functional symptoms. But when you look at this remember that people vary tremendously in how many of these factors are relevant. For some people, many factors are relevant. For others, only one or two are

It is especially important to state that:

YOU DO NOT HAVE TO BE STRESSED. DEPRESSED OR ANXIOUS TO DEVELOP FUNCTIONAL SYMPTOMS

YOU DO NOT HAVE TO HAVE EXPERIENCED AN ADVERSE CHILDHOOD TO DEVELOP FUNCTIONAL SYMPTOMS

There are many people where these factors may be relevant in creating a vulnerability, but there are also many patients where they are not. Doctors can make a mistake in thinking these things must always be present.