Family systems theory was first introduced by Bowen in the 1950s and is a theory of human behaviour that views the family as an emotional unit. The theory suggests that you cannot understand an individual in isolation, and need to consider the rest of their family. This approach has been applied to anorexia nervosa by Minuchin et al. (1978). They developed the psychosomatic family model, which states that dysfunctional families (e.g. those characterised by enmeshment) can trigger anorexia nervosa in a child who is already physiologically vulnerable.