It is not normal for a baby to be 18 months old and not be able to speak. It may be caused by less communication between the parents and the baby, neurological disorders, autism, hearing abnormality, etc. It is recommended to go to the hospital in time to find out the cause of the disease. 1. Less communication between parents and babies: Because parents usually have less communication with babies, so babies can’t speak. 2. Neurological diseases: If the inability to speak is accompanied by abnormal actions, it may be a neurological disease or a genetic metabolic disease, which should be promptly treated in the hospital. 3. Autism: If the infant does not speak and does not play with other infants, has very little attachment to the parents, and seldom communicates with others, he or she may have autism and should go to the hospital for evaluation in a timely manner. 4. Hearing abnormality: If the infant’s response to sound is very weak, there may be a hearing abnormality, which needs to be examined by an ear, nose and throat department. If an infant is 18 months old and can’t speak, parents should seek timely medical attention and actively cooperate with the doctor to find out the cause of the disease, so as to avoid delaying the condition or triggering adverse reactions.