There is no specific test for Parkinson’s disease, and this can make it difficult to diagnose, especially in the early stages. However, certain signs and symptoms may indicate that Parkinson’s is present. The main symptoms of Parkinson’s disease (PD) are tremor, slow movement, and rigidity, or stiffness. The person may also experience pain and difficulty sleeping, among other changes. These happen because of changes in the brain, and especially a clumping of certain types of protein and low levels of dopamine in the brain.