A VPN is not a mental health treatment

Targeted advertising uses identifiers such as cookies and, on networks without a VPN, your IP address. A VPN changes the IP address the site sees and encrypts the path to the VPN server. It does not remove an account you are signed in to, and it does not stop an app from tracking you inside that account.

There is no Oak VPN study that links the product to anxiety, focus, or screen time. If advertising is the problem you want to reduce, the relevant product facts are the logs policy and the device limit, both on the privacy and pricing pages.