Ask any Hispano, addict or not, and you are bound to get an earful.

The first reason is probably the least surprising: the great disparity of wealth in northern New Mexico. The Española Valley itself has never been a wealthy area, but in recent decades tremendous amounts of money have poured into nearby towns, such as Santa Fe and Los Alamos.

Severe drug addiction in poor communities adjacent to affluent ones is a pattern that social scientists have documented worldwide. Some credit the struggle of living in severe poverty while others enjoy lives of ease. Others describe the stigma of crossing the lines between rich and poor, and the abuse that frequently accompanies this crossing.

Anthropologist Philippe Bourgois has documented this pattern of drug use in New York and San Francisco — cities where neighborhoods of extreme wealth and poverty border each other. Harmful public policy weakens local economies and the social welfare system, and leads to the vast disparities in incarceration rates among different races and ethnicities. This creates what Bourgois calls "an aura of apartheid." Even neighborhoods that were once vibrant and healthy are socially and economically marginalized; drug use becomes endemic.

Last year, the World Health Organization launched the Commission on the Social Determinants of Health. Echoing the long-held view of local activists, researchers and health providers, the commission found that living conditions — social, political and economic — play a major role in drug addiction.

"It is poverty and social inequality that kills," says Nancy Krieger, professor of public health at Harvard University. According to Krieger, inequality "deprives individuals and communities of a healthy start in life, increases their burden of disability and disease, and brings early death."

In the Española Valley, the inequality is palpable. Many locals blame the Los Alamos National Laboratories for the region’s deepening chasm between rich and poor. Since the 1940s, the Labs have demanded a local "nonprofessional" work force — maintenance and security crews, for example. Today, the Labs are the largest employer of Valley residents. During rush hour, the Old Los Alamos Highway, which connects Española with the "Atomic City," is bumper-to-bumper with frustrated commuters. Meanwhile, back at home, many of the old family farms lie untended.

Los Alamos is the wealthiest county in the United States, with a median household income of over $93,000 and a below-poverty rate of under 3 percent. Rio Arriba County, which encompasses much of the Española Valley below, is among New Mexico’s poorest counties, with a median income of $29,000. One in five Valley residents lives below the poverty line.

There’s another, less obvious factor that contributes to the spread of heroin through the community. Ironically enough, it is the profound significance of the family in Hispano culture. For generations, family members have lived and worked together. Asked where she lived, a valley resident would not offer the name of a village like Velarde or Alcalde; she would tell you, Los Rendones, or Los Luceros, neighborhoods identifiable by surname because they were composed entirely of relatives. Insular and self-sufficient, the family was the center of social and economic life; it was the conduit through which land, language and tradition were kept alive.

These ties endure in families that share heroin, passing the addiction from one generation to another. In sharp contrast to the mainstream notion of heroin addicts as urban loners, isolated from family or community, in the Española Valley, the family is often the primary domain of heroin use. It is also the primary source of support and care; most cases of heroin overdose are "handled at home" by relatives, never coming to the attention of health workers.

"Family is everything," says 28-year-old Marta Vigil, an addict who is awaiting sentencing for drug trafficking, a charge she denies. Officially, she is under house arrest, and wears an electronic monitor around her ankle. She is using her approved "therapy time" outside of home to "play hooky and have lunch like a normal person." She meets me in a fast-food restaurant in Española.

"Family is everything." I have heard this expression from heroin addicts before. Marta senses my difficulty reconciling the ideal of family togetherness with drug abuse — family members helping each other get drugs, or using drugs together. So she tells me her story.

Marta’s mother was a heroin addict. She remembers terrible nights in her childhood, when her mother agonized in "las malias" — the sharp, shooting pains in the limbs and the profuse sweating brought on by withdrawal. She would be all upset, crying, Marta says. "You’re a kid, and you’re scared they’re gonna die. And, basically, you’ll do anything to make them feel better," she says. "Sometimes, the only thing you feel like you can do is get them high."