Signs due to hyperactivity of stomach and intestines:
Poor feeding and sucking reflex
Vomiting
Diarrhea
Signs due to hyperactivity of autonomous nervous system:
Fever
Sweating
Yawning, stuffy nose, and sneezing
Fast breathing

Causes
The drugs involved can include opioids, selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitor (SNRIs), tricyclic antidepressants (TCAs), ethanol, and benzodiazepines. Opioids may be more likely to cause NAS than other substances due to an increase in its usage. Exposure to heroin and methadone claimed to be correlated with a 60 to 80% occurrence of neonatal withdrawal, whereas buprenorphine has been associated with a lower risk. Neonatal abstinence syndrome does not happen in prenatal cocaine exposure. Prematurity and exposure to other drugs may instead be the cause of symptoms.The main mechanistic pathway of prescribed and illicit substance-induced NAS is the hyperactivity of the central and autonomic nervous system and gastrointestinal tract There are several potential mechanisms and pathways that have been proposed, which includes the interaction between the neurotransmitters and lack of adequate expression of opioid receptors. However, the main pathophysiology of this syndrome remains unknown. Most of the opioid induced NAS are due to opioid exposure during pregnancy for pain relief, misuse, or abuse of prescribed opioids or other medication-assisted treatment of opioid use disorder. Diagnosis
The presence of withdrawal in the neonate can be confirmed by taking a detailed medical history from the mother.
Sedatives
Sedatives such as phenobarbital or diazepam are less effective at symptom control compared to opioids but can reduce length of hospital stay. Clonidine
When compared to opioids, clonidine was just as effective at improving clinical symptoms.Additional medication is used to relieve fever, seizures, and weight loss or dehydration. A 2021 systematic review found low-certainty evidence that phenobarbital lengthened hospital stays but resulted in a return to birth-weight more rapidly. Low-certainty evidence also showed phenobarbital reduced treatment failure rates compared to diazepam and chlorpromazine. There was also low-certainty evidence of increased hospitalization days with clonidine and opioid compared to phenobarbital and opioid. Outcomes
A 2018 meta-analysis reported that newborns diagnosed with NAS are likely to recover with non-medication intervention when roomed with family during their hospital stay compared to newborns diagnosed with NAS that are treated in newborn intensive care unit.Data is limited and more research needs to be conducted to properly evaluate long-term outcomes in children with a prior diagnosis of NAS. However, long-term monitoring into adolescence may be necessary as a 2019 meta-analysis gave evidence of some longterm cognitive and physical side effects associated with prenatal opioid exposure. Epidemiology
United States
A 2012 study  analyzed information on 7.4 million discharges from 4,121 hospitals in 44 states, to measure trends and costs associated with NAS over the past decade.