The investigators will test the value of an internet self-help package (E-Couch) for alleviating social anxiety symptoms in the general population. The investigators will undertake a trial of about 2000 participants to compare the effect of the E-Couch intervention compared to a wait-list control condition. Over a period of 12 months the investigators will measure the effect of using E-Couch self-help on social anxiety symptoms, as well as on mental wellbeing, and other secondary outcomes including quality of life, depression and general anxiety, and their use of other sources of help.

DESIGN The study will involve a large, pragmatic, randomised controlled trial of the internet-based self-directed E-Couch social anxiety module versus a wait-list control condition for the reduction of sub-clinical social anxiety symptoms, among a general population sample recruited using direct-to-consumer advertisements on national websites.

RECRUITMENT Participants in this study will be recruited using advertisements placed on websites such as the NHS website. Individuals expressing an interest in the online advertisement by clicking on a web link will be directed to a University website containing full information on the trial and the opportunity to ask questions of the study team by email or telephone. Participants will be advised in the information sheet that they are free to withdraw at any time without giving a reason and without it affecting their care.

CONSENT Interested participants will be asked to indicate their willingness to participate in the screening and/or the trial by clicking on Yes in response to the online consent questions.

SCREENING Users who provide their consent will be invited to complete screening questions which will determine whether they are eligible for participation in the trial.

INCLUSION AND EXCLUSION Inclusion criteria for this trial include age 18 years and over, resident of England and a score of 13 or more on the SPIN social anxiety measure, and a willingness to provide a working email address and mobile phone number (to respond to a confirmation email and receive reminders). People who are currently receiving therapist-guided treatment for social anxiety disorder will be excluded from participation as will those with a self-reported diagnosis of bipolar disorder or schizophrenia.

MEASURES Following completion of the screening survey eligible participants will be advised that they are eligible to participate in the trial and asked to provide their email address and mobile phone number. Once these details have been submitted they will be advised that in 24 hours they will receive an e-mail providing a link to an online baseline survey. The e-mail will link to a battery of demographic and self-report mental health measures. Measures will be taken at baseline and, for those randomised, at all or most of the follow up points including post-intervention, 3-, 6- and 12-months. At each follow-up point both Intervention and Control participants will receive notification of follow-up measures by email and by text message.

RANDOMISATION Participants who complete baseline measures within one week of receiving the survey link via email, will be randomised using an automated computer algorithm to the E-Couch social anxiety tool (Intervention) or to a Wait list control condition. Participants will be advised of the condition to which they have been allocated.

ACCESS TO INTERVENTION Intervention participants will be asked to set a password associated with their email address, and provided with access to the Intervention. Intervention participants will be encouraged to access and use the self-guided intervention over a period of up to 6 weeks (although they can chose to work through the program at their own pace). Access will be via secure login on the research trial website, using their email address and password.

INTERVENTION The E-Couch social anxiety module which is based on cognitive behavioural therapy principles. This module contains a literacy section and 5 toolkits comprising exposure practice, cognitive restructuring (modifying your thinking), attention practice, social skills training and relaxation. E-Couch is designed to be completed at the participant's own pace. It is free to use, browser-based and widely accessible on a range of connected devices.

CONTROL The Control group will be placed on a wait list to receive the intervention in 12 months.

RISKS The risks to the participants are likely to be minimal. The study uses standard well-tested measures or tools modified from these measures. Participants are referred to a source of help in the Information Sheet in case of distress. The intervention has been employed without problems in publically accessible form across the world since 2008.

Inclusion Criteria:

• Aged 18 or over
• Resident in England
• Willing to provide email address and mobile telephone number
• Able to use a web-based intervention provided in written English
• SPIN score 13 or more (to include those with subclinical symptoms)

Exclusion Criteria:

• Aged under 18
• Not resident in England
• Unwilling or unable to provide email address and mobile telephone number
• Unable to use a web-based intervention provided in written English
• SPIN score <13
• Self-reported history of psychosis (schizophrenia or bipolar affective disorder)
• Receiving therapist-guided support for social anxiety disorder (self-reported)