The exact causes of fabricated or induced illness (FII) are unknown, but previous traumatic experiences in the mother's life seem to play an important role.

Some experts agree that mothers who are involved in FII have a borderline personality disorder. Personality disorders are a type of mental health condition where an individual has a distorted pattern of thoughts and beliefs about themselves, and others. These thoughts and beliefs can lead them to behave in ways that most people would regard as disturbed and abnormal.

Most personality disorders can be traced back to an initial traumatic event during childhood. Many mothers involved in FII also have a history of abuse or neglect, have experienced the loss of a loved one, or grew up in dysfunctional families. Of course, the same is true of thousands of other people who do not go on to abuse their children.

Many people with personality disorders often find a kind of reward in behaviour or situations that other people would find intensely distressing. It is thought that mothers who carry out FII are not doing it out of any genuine malice or dislike of their child, but that they find the situation of their child being under medical care and supervision rewarding and comforting.

Why this should be is still open to interpretation. Many of the women involved in the most serious cases of FII have denied all wrongdoing and refused to co-operate with psychiatric treatment, so there is little available insight into their motives.

One 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 off onto the medical staff.

Another theory is that it is a way for the mother to escape from her own negative feelings and unpleasant emotions. By creating a permanent crisis situation surrounding her child, she can concentrate all her thoughts on her child's treatment, keeping her own negative feelings and emotions at bay.