Abstract
Psoriasis is a chronic inflammatory skin condition that affects 2-9% of the world's population. The well-being of people living with psoriasis is often greatly compromised due to the physical and psychological impact of the skin condition. It is estimated that a third of people living with psoriasis have comorbid obesity which is much more common among them (30-40%) than in the general population (15-20%). Obesity is more prevalent in people with severe psoriasis than those with mild disease and has been linked to sub-optimal treatment response. Both psoriasis and obesity frequently co-occur with depression and anxiety in a bi-directional way, where obesity may drive mental health issues and vice versa. In light of the relationship between psoriasis and obesity, obesity management is a potentially important adjuvant to current psoriasis standard care. However, little is known about the factors that may influence successful weight loss in the context of obesity and psoriasis. Using mixed methods, this thesis aimed to identify the cognitive, emotional, and behavioural factors that are associated with body weight in psoriasis. Such findings would inform future tailored intervention approaches for weight loss that address the idiosyncratic challenges of people living withpsoriasis.
A systematic review of the psychosocial factors associated with body weight in psoriasis found that obesity (assessed as Body Mass Index (BMI) of ≥ 30 kg/m²) is weakly if at all associated with depression and anxiety based on exclusively cross-sectional evidence (N=16). The review highlighted the need to longitudinally explore the association between depression and anxiety with body weight in psoriasis, ideally using more accurate indicators of body fat mass such as waist circumference and controlling for important confounders, consistently overlooked by previous studies. To address these identified gaps in existing evidence, cross-sectional and longitudinal analyses were conducted using routine patient data (N= 326 and N=191, respectively) and waist circumference as an additional outcome to BMI. Through these analyses, the association between depression and anxiety with waist circumference and BMI were evaluated, while controlling for demographic (e.g., age and gender) and illness-related confounders (e.g., treatment type, number of comorbidities, and psoriasis severity). These analyses revealed that depression and anxiety have a small contribution to body weight in psoriasis, whereas psoriasis illness severity and multimorbidity were significantly positively associated with both waist circumference and BMI. Therefore, addressing mood alone is unlikely to be sufficient for weight loss among people living with psoriasis. As raised above, the systematic review also emphasised the stark unavailability of studies looking at the role of other psychosocial such as cognitions related to body weight and psoriasis. Behavioural factors, including coping behaviours like emotional eating in relation to body weight outcomes, are also overlooked by existing evidence. These factors may be particularly central here, beyond the role of depression and anxiety.
As such and given that qualitative studies focused on weight loss in psoriasis have not been conducted, as shown by the review, a qualitative study was deemed necessary to explore in more depth and through a person-centred approach, cognitions, emotions, and behaviours related to weight loss in psoriasis. Semi-structured interviews were conducted with people living with psoriasis and comorbid obesity (N= 24). Participants expressed their feelings of powerlessness in the face of psoriasis and highlighted their lack of clarity regarding the link between psoriasis and obesity. Emotional eating was perceived as a way to cope with the psoriasis burden and associated negative emotions. These findings accentuated the role of illness perceptions and emotional eating in body weight in psoriasis, factors consistently overlooked by quantitative studies in this patient population. Informed by the qualitative study, a cross-sectional study was conducted (N=167) to evaluate the role of illness perceptions and emotional eating in relation to BMI and waist circumference in psoriasis, while controlling for important demographic, lifestyle, and illness-related confounders. Illness perceptions (viewing psoriasis as chronic and treating high body weight and psoriasis as two separate conditions) and emotional eating were positively associated with higher waist circumference and BMI, after controlling for confounders. Similarly to previously described analyses, depression and anxiety were not significantly associated with waist circumference or BMI. These findings corroborate the important role of cognitions and behaviours observed in the qualitative study and the likely complex interplay between cognitions and behaviours related to obesity and psoriasis.
Findings from all these studies suggested that a tailored weight loss intervention for people living with psoriasis should consider the key role of illness perceptions and emotional eating in relation to body weight. Unlike existing weight loss interventions that draw on standard approaches developed for people without comorbid physical health conditions, in the context of psoriasis, a weight loss intervention should consider psoriasis-specific challenges related to body weight, likely leading to more optimal weight-related outcomes.
| Date of Award | 1 Sept 2023 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Rona Moss-Morris (Supervisor), Federica Picariello (Supervisor) & Catherine Smith (Supervisor) |