Breast Cancer Patients' Cognitive Symptoms After Information About Chemotherapy-Related Cognitive Symptoms

Six items of the revised Medical Outcomes Study - cognitive functioning subscale (MOS-cog; Stewart & Ware, 1992) to measure the perceived frequency of cognitive symptoms. Participants indicated the frequency of experiencing a range of day-to-day problems in six aspects of cognitive functioning during the past week (including today). Higher mean scores indicate better perceived cognitive functioning (range 0-100).

Two items of the M.D. Anderson Symptom Inventory Multiple Myeloma module (MDASI-MM part 1; Cleeland et al., 2000; Jones et al., 2013) to measure the perceived severity of cognitive symptoms. Patients reported the severity of two cognitive symptoms at their worst in the last 24 hours on a 0-10 scale, with 0 being 'not present' and 10 being 'as bad as you can imagine': difficulty remembering and difficulty paying attention (concentrating). Higher mean scores indicate more severe symptoms.

Online, adapted version of the Groningen Fifteen Words Test (Rey, 1964) measuring immediate recall (range 0-45), delayed recall (range 0-15) and recognition (range 0-30). Higher scores indicate better performance.

Online version of the Trail Making Test (TMT; Reitan & Wolfson, 1985) part A and B (and TMT-B to TMT-A ratio B/A) to measure the speed of information processing and executive functioning. The score on each part represents the amount of time in seconds required to complete the task. Higher scores indicate worse information processing and executive functioning.

Dutch version of the Hospital Anxiety and Depression Scale (HADS; Spinhoven et al., 1997; Zigmond & Snaith, 1983) to measure levels of anxiety. Higher sum scores (range 0-21) indicate higher levels of anxiety.

Dutch version of the Hospital Anxiety and Depression Scale (HADS; Spinhoven et al., 1997; Zigmond & Snaith, 1983) to measure levels of depression. Higher sum scores (range 0-21) indicate higher levels of depression.

Twelve items of the thirteen-item core M. D. Anderson Symptom Inventory (MDASI; part 1; Cleeland et al., 2000) to measure the perceived severity of other cancer-related symptoms. Participants reported the severity of twelve symptoms at their worst in the last 24 hours hours on a 0-10 scale, with 0 being 'not present' and 10 being 'as bad as you can imagine.' Difficulty remembering was excluded. Higher mean scores indicate more severe symptoms.

Participants indicated on one item (range 1-5) at the end of the T2 survey whether they had knowledge about the potential cognitive side-effects of cancer treatment prior to the experiment to measure pre-existing knowledge. Higher scores indicate more pre-existing knowledge.

An adapted version of two items of the M. D. Anderson Symptom Inventory Multiple Myeloma module (MDASI-MM; part 1; Cleeland et al., 2000; Jones et al., 2013) to measure the expected severity of cognitive symptoms during the next weeks (range 0-10). Higher scores indicate expectations of more severe cognitive symptoms.

An adapted version of four items of the M. D. Anderson Symptom Inventory Multiple Myeloma module (MDASI-MM; part 1; Cleeland et al., 2000; Jones et al., 2013) to measure the expected severity of other cancer-related symptoms during the next weeks (range 0-10). Higher scores indicate expectations of more severe other cancer-related symptoms.

Five modified and translated items from the effort subscale of the Intrinsic Motivation Inventory (IMI; Ryan, 1982; Ryan & Deci, 2000) to measure the levels of motivation during the neuropsychological tasks (range 1-5). Higher mean scores indicate higher levels of motivation.

Four modified and translated items derived from the test anxiety subscale of the Motivated Strategies for learning Questionnaire (Pintrich & De Groot, 1990) to measure the levels of worrying about cognitive test performance (range 1-5). Higher mean scores denote higher levels of worries.

Seven items of the intrusion subscale of the Dutch version of the Impact of Events Scale (Horowitz, Wilner, & Alvarez, 1979; Van der Ploeg et al., 2004) to assess the levels of intrusion of cancer related stressful thoughts (range 0-28). Higher sum scores indicate higher intrusion when confronted with the stressful experience of being treated for cancer.

Eight translated and adapted items derived from the 10-item Stigma Consciousness Questionnaire to measure the extent to which patients expect to be stereotyped by others (Brown & Pinel, 2003; cf. Jacobs, Das, & Schagen, 2017; range 1-5). Higher mean scores indicate higher levels of stigma consciousness.

Three adapted and translated items from the math identification subscale of the Social Identities and Attitudes Scale (SIAS; Picho & Brown, 2011), to measure the extent to which participants identify with the domain of 'cognition' and the level of importance of their cognition (range 1-5). Higher mean scores indicate higher levels of domain identification.

Two newly developed items and four items derived and adapted from Doosje and colleagues (Doosje, Ellemers, & Spears, 1995), Spears and colleagues (Spears, Doosje, & Ellemers, 1997), and Quayle (2011) to measure the level of group identification, that is to what extent participants identify with other (ex) cancer patients (range 1-5). Higher mean scores indicate higher levels of group identification.

Information monitoring was measured by one item that asked patients how often during the past weeks they searched for health- and cancer related information (range 0-4). Higher scores indicate higher levels of information monitoring.

One item to indicate which information sources participants used (twelve options; for example information leaflets yes/no).

One item to assess what information content participants looked for (six options; for example information about chemotherapy side-effects yes/no).

At twelve months follow-up (T2), stereotype self-relevance was measured using one item that assessed perceived self-relevance of the chemotherapy-impairs-cognition stereotype: 'To what extent does the phenomena 'Chemo brain' apply to you?' (range 1-5). Higher scores indicate higher levels of self-relevance.

At twelve months follow-up (T2), two items asked participants to indicate the extent to which they attributed their own and others' cognitive symptoms to chemotherapy (range 1-5). Higher scores indicate higher levels of attribution of cognitive symptoms to chemotherapy.