Could i develop mental illness from seeing abuse for years?

Maybe: People can develop several types of mental illnesses from witnessing a variety of types of abuse, depending on several factors, with depression and anxiety disorders being the most common. Factors are things such as age and support during and after the trauma, genetics, etc. If you've witnessed abuse, are having symptoms, I would urge you to please seek psychiatric attention for an evaluation.

Dr Weixel and another doctor agreed

It's possible.: It is possible that you could develop a mental illness from being exposed to abuse, witnessing it in forms such as domestic violence, etc. If you are concerned, then speak to a mental health professional.

Vicarious Trauma: Abuse for the victim and witness can be traumatic to both. For the witness it is called vicarious trauma. All can result in acute stress disorder and Posttraumatic Stress Disorder (PTSD). If you are experiencing PTSD symptoms such as reexperiencing via intrusive memories and flashbacks as well as other PTSD symptoms (e.g avoiding trauma-related objects), see a mental health professional

Dr Juchau and another doctor agreed