The current study utilised a large sample of treatment-seeking adults at an out-patient ED service to investigate ED symptomatology, psychological distress and psychosocial function between EO-AN, TO-AN and LO-AN patients. Our hypotheses that those with EO-AN would demonstrate increased ED symptomatology, psychological distress and more impaired psychosocial function than those with TO-AN or LO-AN were partly supported. There were no differences in BMI or AN subtype between the three groups. However, the EO-AN group reported a significantly longer illness duration than both TO-AN and LO-AN groups. After controlling for the impact of illness duration, the EO-AN group reported significantly increased ED symptomatology and dysmorphic concern than those with LO-AN. Moreover, the EO-AN group demonstrated significantly decreased cognitive flexibility as compared to both the TO-AN and LO-AN groups. There were no differences between groups on psychological distress or other psychosocial outcomes.
In accordance with prior research, our observations that patients with EO-AN reported a longer illness duration, higher ED symptomatology and dysmorphic concern than those with LO-AN, which indicates that EO-AN may present with a more severe form of illness (25, 38). The increased severity in ED symptomatology demonstrated by the EO-AN group was consistent across all domains of the EDE-Q aside from restraint, which demonstrated a trend towards being increased in the EO-AN group. This supports previous findings of more severe ED behaviours, such as complete refusal of oral intake and more severe restriction, in patients with EO-AN. Similarly, distorted self-perception of body image, a key feature of AN (29, 39), was significantly higher in those with EO-AN compared to LO-AN, consistent with previous findings (25). Contributing factors to the increased ED psychopathology seen in the EO-AN group may include various biological and environmental factors, which differ across development. These include pressures experienced by younger patients, such as changes related to puberty and increased susceptibility to external negative influences on body image perception and idealisation (40). It has been postulated that onset of AN prior to puberty may intensify perceived body image ideals (41), whereby the associated increase in adipose tissue and widening of the hips in adolescent females during puberty may exacerbate cognitions related to thin body ideal (18). Moreover, experience of body change in the EO-AN group may also be substantially influenced by social media ideals, peer relationships and the emergence of gender roles (42, 43). The importance of physical attractiveness and the consolidation of sexuality have been demonstrated to influence self-concept and psychological profile at this stage of development (44). Moreover, rates of teasing and bullying have been demonstrated to be higher in EO-AN than LO-AN (21), supportive of the theory that early developmental trauma may contribute to increased levels of psychological distress as well as enduring patterns of body image disturbance (45, 46).
Another feature that is widely associated with AN is cognitive inflexibility (47, 48), which involves deficits in the ability to adapt thinking or attention to shifting goals or environmental stimuli (49). The current study demonstrated significantly lower levels of cognitive flexibility in patients with EO-AN compared to both TO-AN and LO-AN, supportive of previous findings of lower metacognitive abilities in patients with EO-AN (50). Decreased cognitive flexibility, as demonstrated in the EO-AN group, may manifest in heightened rigidity in thinking and be reflected in more severe ED cognitions (51), resulting in behaviours such as categorisation of food and calorie counting (52). Moreover, cognitive inflexibility may also lead to problems in finding solutions to managing difficulties and distress, therefore maintaining maladaptive thoughts and behaviours in AN (52), contributing to the challenges faced in psychotherapeutic interventions in this patient group. Specifically, diminished cognitive flexibility may be a limiting factor in cognitive behaviour therapy interventions, whereby a lack of communication of alternatives may lead to poor engagement with treatment and suboptimal outcomes of therapy. Indeed, cognitive inflexibility and obsessional thinking have been shown to predate the onset of AN, persist over the course of the illness and contribute to later relapses in adulthood (53, 54).
Investigations into psychological distress in the current study found no significant differences between the three AOO groups in measures of depression, anxiety and stress. However, there was a trend for increased anxiety in individuals with EO-AN compared to TO-AN and LO-AN, which may be due to the abovementioned developmental and environmental influences experienced by this group of patients. It has also been suggested that EO-AN is under stronger influence of biological processes such as pre-illness alterations in neural circuits (55), which may lead to higher expression of distress and anxiety symptoms. Psychological distress was universally high across all three groups, which is representative of the established high rates of comorbid anxiety and depressive disorders across varying AOO groups in AN (24, 38, 56, 57).