Spasticity is usually caused by central nervous system injuries, such as brain injuries or spinal cord injuries. Spasticity is a little different from stiffness.
One of the things that was identified through research is that patients with cerebral palsy have higher rates of depression and anxiety than you would see in the general population.
"Cerebral palsy is primarily a motor impairment so it's really important to look at what the child’s motor function is. Are they developing on the trajectory of a child who has cerebral palsy or are they developing as we would expect a baby to develop? "
To give you an idea about genetic variation between each of us, there are about three million differences in our genetic code. They go to influence the color of our hair and the color of our eyes, the way we walk.