Efficacy of a Positive Psychological Intervention in Patients With Eating Disorders

This scale measures positive and negative expectancies about future events. It consists of 20 statements referring to negative expectancies and 10 statements referring to positive expectancies. Participants answer on a 7-point scale (Not at all likely to occur - Extremely likely to occur). Some studies have found an appropriate levels of internal consistency for positive and negative expectancies (α=0.80-0.82 y 0.91, respectively).

To measure affect, the Spanish adaptation of the Positive and Negative Affect Scale was used (PANAS, Sandín et al., 1999; Watson, Clark & Tellegen, 1988). This instrument is composed of 20 items: 10 items measuring positive affective states and 10 items measuring negative affect states. Participants rate on a five-point scale (from "Not at all" to "Extremely") the degree to which they usually feel a specific affective state. PANAS is one of the most widely-used instruments to measure affect because it shows excellent psychometric properties (Cronbach Alpha's from 0.87-0.91).

This scale measures positive and negative expectancies about future events. It consists of 20 statements referring to negative expectancies and 10 statements referring to positive expectancies. Participants answer on a 7-point scale (Not at all likely to occur - Extremely likely to occur). Some studies have found an appropriate levels of internal consistency for positive and negative expectancies (α=0.80-0.82 y 0.91, respectively).

This questionnaire evaluates a general dimension and three aspects of self-efficacy: initiative, persistence and effort. The internal consistency coefficients for the subscales varied from excellent to good (Initiative = 0.83; Effort =0.77; Persistence = 0.80; and Total = 0.86).

This instrument evaluates dispositional hope. It is composed of 12 items (Agency: 4 items; Pathways= 4 items; Fillers= 4 items), with an 8-point Likert scale ranging from 1 (definitely false) to 8 (definitely true). Internal consistency coefficient (Cronbach's alpha) for the total scale was excellent (.89).

This instrument assesses participants' initial motivation to do the assigned exercise. It explores the different reasons for the participants to carry out the exercise. The scale is composed of 4 items whose goal is to find out whether the motivation is intrinsic or extrinsic. A total score is obtained by subtracting the two extrinsic motivation scores from the two intrinsic motivation scores.

This scale assesses the neuroticism level of the individual, showing if he is stable or neurotic. This subscale is composed by 12 items of dicotomic response (yes-not). Regarding psychometric properties, Eysenck and Eysenck (1997) got an alpha coefficient between 0-73 and 0.82.

This questionnaire assesses a broad range of attitudes and behaviors related to anorexia nervosa. It is composed of 26 items rated on a 6-point Likert scale from 0 (never) to 6 (always), based on the frequency with which the individual carries out the behavior or has the thought described by the item. The instrument has shown excellent psychometric properties (Toro, Castro, Garcia, Perez & Cuesta, 1989; Rivas, Bersabé, Jiménez & Berrocal, 2010).

This scale encompass ninve primary dimensions of psychopathological symptoms: psychoticism, somatization, depression, hostility, phobic anxiety, obsessive-compulsive, anxiety (panic), paranoid ideation, and nervous tension. Each BSI item is rated on a 5- point scale (0 to 4) according to manifestations of symptoms in the last 30 days (ranging from "not at-all" to "extremely").