Participants

Patients were recruited at the Psychiatric University Clinic of Parma, a public community-based mental health service, from the 31st of January 2013 to the 26th of November 2014. A psychiatrist (PO) evaluated patients using a suitably structured socio-demographic interview to collect anamnestic and data concerning therapy and illness course.

Sample size was based on a previous study (Korn et al., 2014), which found a negative correlation between the Update Bias and BDI scores of r = −0.50 (p<0.001). The required sample size based on this was n = 23 for an alpha of 0.05% and 80% power, beta = 0.80 (Faul et al., 2007). As we expected up to 50% dropout over 5 years, we recruited 45 bipolar patients (19 female, 42.2%) aged between 20 and 80 (mean = 45.87; s.d. = 13.09). Fourteen of the patients had performed the belief update task once before for another study approximately 4 months prior, but using different stimuli. No difference emerged between those that performed the task in the past and those that did not.

The study design is observational and prospective. The patients were followed-up with psychiatric visits at the hospital approximately every 2 months (min = 0.25 months, max = 3 months) for 5 years from enrolment (until December 2019) by the same psychiatrist (PO) who is trained in the administration of the SCID-5. The follow-up visits were part of the clinical practice in an outpatients’ service specialized in bipolar disorder. The occurrence of new episodes, registered at the time of the visit, was discussed and confirmed by the clinicians according to the DSM-5 criteria. Error could occur if a patient happened to relapse and recovered between the visits (i.e. within the 2-month gap) and the clinician had failed to record these events. This, however, is unlikely as the average duration of a mood episode is 4 months (Tondo et al., 2017). Patients for whom there was no contact for a period longer than 6 months were dropped from the study (n = 9) and their data were not included in the survival analysis. This resulted in a final sample of 36 subjects. All participants gave informed consent prior to testing. The local ethics committee (Comitato Etico per Parma) approved the study protocol in accordance with the Helsinki Declaration.

Participants were invited to participate in the study if they: (1) Fulfilled the diagnostic criteria for Bipolar Disorder I or II at the Structured Clinical Interview for DSM IV TR Disorders (First et al., 2002) in full remission. (2) Did not satisfy the criteria for Rapid Cycling (i.e. more than four episodes/year) (American Psychiatric Association, 2013); (5) Did not have any other major axis I diagnosis (i.e. Schizophrenia spectrum disorder, Obsessive Compulsive Disorder, Panic Disorder, Generalized Anxiety Disorder, Post Traumatic Stress Disorder, Anorexia Nervosa, Binge Eating Disorder). Specific Phobias and Personality Disorders were not considered because they are outside the study’s aim; (6) Did not reveal substance abuse/dependence or addictive disorder in the previous three months; (7) Did not show cognitive impairment, defined as score of less than 25 on the Mini Mental State Examination (Folstein et al., 1975).