The first symptoms of Alzheimer's disease on top of forgetfulness are almost across the board mental symptoms. People with depression, two and a half times more likely to develop Alzheimer's but it goes every mental disorder. Unexplainable depression, anxiety, personality changes, getting obsessive for no reason. Depression can be the first sign of cancer before they even know they have cancer. And what I'm here to say is that mental illness, like real mental disorder,. do not have disorders of their brain. The people who have mental disorders across the board have much higher rates of Alzheimer's Disease.