Infants Dependent on Opioids Rising Faster in Rural Areas, Study Finds Rates are rising everywhere, faster in rural areas than in urban areas.

 -- The numbers of infants born affected by opioids is rising, especially in rural areas, according to a new study published today in the medical journal JAMA Pediatrics.

The findings fit with previous studies that have found higher rates of opioid abuse in rural areas as compared to urban areas, said study co-author Dr. Stephen Patrick, assistant professor of Pediatrics and Health Policy at Vanderbilt University School of Medicine.

"It highlights a need to focus on the unique needs of rural communities and to understand why the opioid epidemic has disproportionately affected rural communities," Patrick told ABC News.

Rates of infants dependent on opioids, identified as "neonatal abstinence syndrome," or NAS, rose dramatically between 2004 and 2013, most noticeably in rural areas, according to this study. The researchers looked at almost 24,000 infants in samples of hospital discharge data, part of a database sponsored by the U.S. Department of Health and Human Services' Agency for Healthcare Research and Quality.

Researchers from multiple institutions, including University of Michigan, Vanderbilt University School of of Medicine and University of Minnesota examined the information from the National Inpatient Sample.

NAS occurs in newborns, who are exposed to opioids either in utero or shortly after birth. Symptoms are "manifested by central nervous system irritability, autonomic overreactivity, and gastrointestinal tract dysfunction," according to the U.S Centers for Disease Control and Prevention (CDC).

As the opioid crisis has continued to grow in the U.S., much of the attention has focused on rising rates of fatal overdoses.

But NAS is another example of the how the opioid crisis is also causing other public health problems, including additional strains on foster care from children born to drug users, according to Dr. Caleb Alexander, co-director for the Johns Hopkins Center for Drug Safety and Effectiveness.

"They're all less appreciated affects and affects that are less commonly linked" to the opioid crisis, Alexander told ABC News. "Yet they are a direct consequence of it."

Researchers reviewed every birth documented in the National Inpatient Sample between 2004 and 2013 and identified 4,192 infants in rural areas with NAS and 19,752 infants in urban areas with NAS.

While rates of NAS increased in both rural and urban areas, it was rural areas that saw the most dramatic rise -- from 1.2 NAS cases per 1000 hospital births in 2004 to 7.5 NAS cases per 1,000 hospital births in 2013.

In urban areas, however, the rate of NAS cases rose at a slower rate, from 1.4 per 1,000 hospital births in 2004 to 4.8 NAS cases per 1,000 hospital births in 2013, according to the study.

Alexander said many women taking illicit opioids may not be aware of the danger the drug can pose to a developing fetus or have difficulty getting into treatment programs due to lack of insurance, lack of knowledge about treatment centers or lack of access to treatment facilities.

"This one it is particularity heartbreaking," Alexander said, "because these newborns are society's most vulnerable members."

Researchers acknowledged that increasing awareness of the opioid crisis, and therefore more doctors monitoring occurrences, could have been a contributing factor in the number of babies who have been documented as addicted to opioids. However, they found it was unlikely that increased awareness alone could fully explain the dramatic increase.

Overall opioid use, across age ranges, has continued to rise. In 2014, the U.S. Centers for Disease Control and Prevention (CDC) estimated that 28,000 people died due to opioid-related overdoses -- half of them from prescription drugs.

Last week, the CDC released data that found deaths by heroin overdose alone had surpassed the number of people who had died due to a firearm homicide.