Cholecystokinin (CCK) is a brain-gut peptide with broad biological activities. It is one of the main regulating hormones in the digestive system, and it plays an important physiological role in the central and peripheral nervous system as a neurotransmitter or a neuromodulator. Recently, many reports have demonstrated that there were a number of SNPs on CCK gene, of which -45C/T and -196G/A showed certain correlation with a variety of psychiatric states such as schizophrenia, depressive disorder, suicidal behavior, Parkinson's disease, etc. These SNPs may be used in paternity testing and personal identification. In addition, it may also become one of the auxiliary indicators in some special cases of forensic pathology.