The current study will utilise a randomised controlled trial design, where the majority (n=240) of participants will be allocated to the immediate treatment (internet-delivered CBT for either depression or anxiety), and a smaller number (n=120) will be allocated to a waiting list. The waiting list group will receive treatment after an eight week wait. This design helps us to understand that any changes in symptoms in the treatment group will be likely due to the treatment they received compared to the waiting list.