Mnemophobia is the fear of memories, either by remembering past events or fearing memory loss during mental diseases like Alzheimer's. Like most other phobias, this is traced from memorable traumatic experiences in the past. Sufferers tend to avoid conversations about those negative experiences and may even abandon friends (current or former).
The symptoms include the urge to flee, feeling like losing one's mind, loss of control, suicide thoughts, having trust issues, weeping, screaming, and a psychotic break in severe cases. This phobia can be treated using exposure response therapy performed by psychologists, in which patients gently face the memories they fear to demonstrate that what they fear is not as harmful as patients may believe.
Trivia[]
There's also the FNAF fangame series called "Mnemophobia". It's actually the same name that have this phobia.