There were issues with the technical service provider of the platform iSupport-Portugal; the platform and its backoffice should be implemented by another service provider. A pilot study was conducted following the protocol of the full trial.

Informal caregivers of people with dementia are at greater risk of developing physical and mental health problems when compared to the general population and to informal caregivers of people with other chronic diseases. Internet-based interventions have been explored in its potential to minimize the negative effects of caring, accounting for their ubiquitous nature, convenient delivery, potential scalability and presumed (cost)effectiveness. iSupport is a self-help online program developed by the World Health Organization to provide education, skills training and support to informal caregivers of people with dementia. This intervention study aims to determine the effectiveness of a Portuguese culturally adapted version of iSupport to decrease caregiver burden, symptoms of depression and anxiety, and to improve quality of life, positive aspects of caregiving and general self-efficacy. The study has two arms: access to "iSupport" for three months or access to an education-only e-book. iSupport is grounded in problem-solving and cognitive behavioral therapy techniques and it consists of 23 lessons organized around 5 modules: 'Introduction to dementia'; 'Being a carer', 'Caring for me', 'Providing everyday care', and 'Dealing with behaviour changes'.

One hundred and eighty four participants will be recruited by referral from national Alzheimer's associations. Participants will be included if they match the following criteria: being 18 years or older and provide e-consent; being a self-reported non-paid caregiver for at least 6 months; caring for a person with a formal diagnosis of Alzheimer's disease; being skilled to use internet; and experience a clinically relevant level of burden or depression or anxiety symptoms. Data is collected online, resorting to self-administered instruments, at baseline, 3 and 6 months after baseline. A two-sided alternative hypothesis was assumed for this study: Mean caregiver burden at 3 months after baseline is different in informal caregivers of people with dementia assigned to the iSupport program as in those assigned to a minimal education-only intervention. Findings from this intervention study will offer evidence to support an informed decision making on scaling up iSupport as a new intervention program with minimal costs aimed at minimizing the psychological distress of informal caregivers of people with dementia in Portugal and elsewhere.

Inclusion Criteria:

• Portuguese adults (≥18 years) (as self-reported and reported by professionals in the referral process);
• Giving consent to participate (Electronic Informed Consent);
• Providing non-paid care for at least 6 months at the time of the recruitment (as self-reported and reported by professionals in the referral process);
• Caring for a person holding a formal diagnosis of dementia (as reported by professionals in the referral process);
• Be skilled to use the internet (as self-reported and reported by professionals in the referral process);
• Experiencing either a clinically relevant level of subjective burden, as determined by a total score ≥ 21 on the Zarit Burden Interview or depression or anxiety symptoms, determined by a score ≥ 8 in at least one of the subscales of the Hospital Anxiety and Depression Scale.

Exclusion Criteria:

• Unable to comprehend written Portuguese (as reported by professionals in the referral process);
• Not having access to a device with internet connection at least twice a week (as self-reported and reported by professionals in the referral process);
• Declaring to care for a person in institutional care (e.g. nursing home or continued care unit) (as self-reported and reported by professionals in the referral process).

Participants are not unaware of the intervention received as they are active parts of the intervention. The data analyst will be blinded to the intervention assigned to the participants. Data collection at baseline and outcomes assessment are carried out in a computerized manner via study online platform and resorting to self-report/self-administered instruments, thus the researcher has no control or influence over the measurements.