Final answer:
Decreased pseudocholinesterase can be caused by conditions such as Parkinson's disease, certain insecticides, and drugs used for Alzheimer's and myasthenia gravis.
Step-by-step explanation:
Decreased pseudocholinesterase can be caused by various conditions. One condition is Parkinson's disease, which is a degenerative disorder of the central nervous system. In this disease, the death of neurons in the midbrain leads to decreased levels of pseudocholinesterase, resulting in muscle tremor, muscle rigidity, slowness of movement, and other symptoms. Additionally, certain insecticides and drugs used for Alzheimer's and myasthenia gravis can also decrease pseudocholinesterase activity, affecting nerve transmission.