It's not fully understood why some parents or carers fabricate or induce illness in their child.
The parent or carer may gain something, such as attention or support, from the child being treated as ill. Or they may have anxiety or incorrect beliefs about the child's health.
It's likely the parent or carer will have a mental health condition or a history of previous traumatic experiences that helps to explain their behaviour.
Child abuse
Research has found some parents and carers who were known to have fabricated or induced illness in their child were victims of physical and sexual abuse during their own childhood.
But most people who are abused as children do not go on to abuse their own children.
Previous medical history
One or both parents may have a history of self-harm or drug or alcohol misuse.
Some case studies also revealed that the mother may have experienced the death of another child, or a difficult pregnancy.
Personality disorder
A high proportion of parents and carers involved in FII have been found to have a personality disorder and, in particular, a borderline personality disorder.
Personality disorders are a type of mental health problem where a person has a distorted pattern of thoughts and beliefs about themselves and others. These distorted thoughts and beliefs may cause them to behave in ways that most people would regard as disturbed and abnormal.
A borderline personality disorder is characterised by emotional instability, disturbed thinking, impulsive behaviour, and intense but unstable relationships with others. It's important to note that not everyone with borderline personality disorder goes on to abuse their children.
Sometimes, people with personality disorders find reward in behaviour or situations that other people would find intensely distressing. It's thought that some parents or carers who carry out FII find the situation of their child being under medical care rewarding.
Other parents or carers who've been involved in FII have reported feeling a sense of resentment towards their child because they have a happy childhood, unlike their own.
Anxiety disorder
Some parents have an anxiety disorder that makes them have unfounded anxieties about their child's health.
Some parents also have health anxiety about themselves.
They may be motivated by genuine worries about the child, but because these worries are unfounded their behaviour can harm the child.
Somatic symptom disorder
Some parents have a somatic symptom disorder, or somatoform disorder.
This means they genuinely feel pain or other symptoms, but it's related to underlying emotional difficulties rather than physical health conditions.