It's not fully understood why some parents or carers fabricate or induce illness in their child.
However, it's likely the parent or carer will have a history of previous traumatic experiences.
Recent studies have shown that mothers who carry out the abuse have abnormal "attachment" experiences with their own mothers, which may affect their parenting and relationship with their children. An example of this is repeatedly seeing a doctor to satisfy an emotional need to get attention for the child.
A study found that almost half of mothers who were known to have fabricated or induced illness in their child were victims of physical and sexual abuse during their own childhood.
However, it's worth noting that most people who are abused as children do not go on to abuse their own children.
Some case studies also revealed that the mother may have experienced the death of another child, or a difficult pregnancy.
A high proportion of mothers 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 all mothers with borderline personality disorder go 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 mothers who carry out FII find the situation of their child being under medical care rewarding.
Other mothers 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.
A further theory is that FII is a kind of role playing.
It allows a mother to adopt the role of a caring and concerned mother, while at the same time allowing her to pass the responsibility of caring for a child on to medical staff.
Another theory is that FII is a way for the mother to escape her own negative feelings and unpleasant emotions.
By creating a permanent crisis situation surrounding her child, she's able to focus her thoughts on the treatment of her child, while keeping her own negative feelings and emotions at bay.