Search strategy and data sources

We searched the following databases, from 1999 until May 2021, for published studies written in English: MEDLINE and MEDLINE in-process (via Ovid); PsycINFO (via Ovid), NIH Clinical Trials; Cochrane Central Register of Controlled Trials (CENTRAL); Web of Science and PubMed. Following establishment of a provisional list of studies, their citation indexes were checked for any similar studies not captured by the initial search,⁵¹ alongside hand-searching the reference lists of other reviews covering analogous intervention-types (e.g. internet-facilitated interventions for unpaid caregivers of patients with similar conditions).

A search strategy using key search terms compiled through a combination of the study authors’ (AH, JS) expertise and consultation of the extant literature was formulated. Terms were devised using the Population (e.g. caregiv*/neurodegener*/informal); Intervention (iPhone/digital/technology); Comparison intervention and Outcome measures (PICO) framework,⁵² concentrating on population and intervention terms, to ensure a highly sensitive search. Searches were executed using a mixture of entered keywords and existing Medical Subject Heading terms (MeSH), which were ‘exploded’ to encompass related terms. Truncation conventions, common abbreviations and Boolean operators were utilised where appropriate in order to optimise the search's sensitivity. For each database, the search strategy was customised. A complete list of search terms for each database are detailed in Appendix 2.