NYU study identifies teens at risk for hashish use

The recent increase in popularity of marijuana use coupled with more liberal state-level polices has begun to change the landscape of adolescent marijuana use. More potent forms of marijuana, such as hashish, may present a threat to adolescent health. A wealth of research has been conducted to examine risk factors for teen marijuana use; however, studies rarely differentiate between different forms of marijuana.

A new study by researchers affiliated with New York University’s Center for Drug Use and HIV Research (CDUHR), was among the first to examine prevalence and correlates of hashish use in a nationally representative sample of US high school students.

Analyses focused on data collected from high school seniors (weighted N=10,597) in years 2007-2011 (2011 was the last year recreational marijuana use was still illegal in all US states). The researchers determined how sociodemographic factors and reasons for marijuana use were related to recent (12-month) hashish use.

“Nearly one out of ten teens reported ever using hashish and it was used by a quarter of lifetime marijuana users,” said Joseph J. Palamar, PhD, MPH, a CDUHR affiliated researcher and an assistant professor of Population Health at NYU Langone Medical Center (NYULMC). “Hashish and other marijuana use tended to share many of the same correlates; however, our results found that risk factors for regular marijuana use were often much stronger risk factors for hashish, a much more potent form of the drug.”

The study, “Prevalence and Correlates of Hashish Use in a National Sample of High School Seniors in the United States,” used data from Monitoring the Future (MTF), a nationwide ongoing annual study of the behaviors, attitudes, and values of American secondary school students. The MTF survey is administered in approximately 130 public and private schools throughout 48 states in the US. Roughly 15,000 high school seniors are assessed annually.

Both hashish and non-hashish marijuana can be smoked, vaporized, or cooked in food. Hashish can be used either in its natural state or converted into a more concentrated oil. However, compared to other marijuana, hashish usually contains a higher concentration of Δ9-tetrahydrocannabinol (THC), which is the most potent psychoactive cannabinoid. While a typical marijuana cigarette (“joint”) contains only 0.5-5% THC, hashish tends to contain 2-20% with some estimates as high as 50%.

The difference between marijuana and hashish goes far beyond country of origin. Marijuana is the most common and least powerful form of cannabis. It is made from dried plant leaves and flowers. Most of American cannabis is strictly the flower or bud of the plant and does not contain whole plants. THC (tetrahydrocannabinol) is the main active ingredient in marijuana that acts upon the nervous system. Marijuana usually contains a maximum of 25% to 30% THC.

Hashish, also known as hash, is made by eliminating plant material and collecting the trichomes from the flower tops of female cannabis plants. These flowers, or ‘heads’, are the most potent parts of the plant. As a result, the THC content of hashish typically varies from 20% to 60%. There are two common methods for producing hash:

  In Morocco and Lebanon, hashish is made by sifting the mature cannabis tops through a series of fine sieves until a resinous powder remains. This powder is compressed and heated to allow the resins to melt, binding the remaining vegetable matter. The resin is compressed into blocks sealed with cellophane or cloth.
  In the Indian sub-continent, hashish is made by rubbing the resinous tops of the plant with the hands or a leather apron. This allows the resins to stick together. These are then scraped off the skin or leather and rolled into lumps of various sizes, and later compressed into blocks.

“Another key finding was that other drug use was a robust risk factor for hashish use,” said Dr. Palamar. “Other illicit drug use, regular cigarette smoking, and frequent alcohol use each increased the risk for hashish use; however, a main finding was that as frequency of other marijuana use increased, so too did risk for recent hashish use.”

NYU study identifies teens at risk for hashish use Females were consistently at low risk for hashish use, but not general marijuana use. In some respects, these findings corroborate previous research that females tend to be at low risk for “harder” drugs than males. Hashish tends to be much more potent than other marijuana, and this study has determined that it is primarily the males that are at higher risk for use of this more potent form of the drug.

“Interestingly, our research found that students using marijuana because they identified as being “hooked” on it nearly doubled the odds for hashish use,” said Dr. Palamar. “Since it is the more frequent marijuana users and those who feel they are hooked who are more likely to use hashish, in some instances hashish use can be used as an indicator of severity of marijuana use.”

These findings can inform prevention and harm reduction in a time of increasing popularity of marijuana use and increasing rates of use of hashish products.


Researcher Affiliations: Joseph J. Palamar, PhD—NYULMC, Department of Population Health; NYU CDUHR; Joseph J. Palamar1,2, Lily Lee 3 and Michael Weitzman4,5,6

1 Department of Population Health, New York University Langone Medical Center, New York, NY
2 Center for Drug Use and HIV Research, New York University, New York, NY
3 Brooklyn College, City University of New York, Brooklyn, New York
4 Departments of Pediatrics and 5Environmental Medicine, New York University Langone Medical Center
6 The Global Institute for Public Health, New York University, New York, NY

Declaration of Interest: The authors declare no conflict of interest.

Acknowledgements: The authors would like to thank the principal investigators of Monitoring the Future (PIs: Johnston, Bachman, O’Malley, and Schulenberg) at The University of Michigan, Institute for Social Research, Survey Research Center, and the Inter-university Consortium for Political and Social Research for providing access to these data. Monitoring the Future data were collected through a research grant (R01 DA-01411) from the National Institute on Drug Abuse (NIDA). Michael Weitzman was supported in part, by NIH/NCI 3 P30 CA016087-33S1. The project otherwise was not funded.


The mission of the Center for Drug Use and HIV Research (CDUHR) is to end the HIV and HCV epidemics in drug using populations and their communities by conducting transdisciplinary research and disseminating its findings to inform programmatic, policy, and grass roots initiatives at the local, state, national and global levels. CDUHR is a Core Center of Excellence funded by the National Institute on Drug Abuse (Grant #P30 DA011041). It is the first center for the socio-behavioral study of substance use and HIV in the United States and is located at the New York University College of Nursing.

About NYU Langone Medical Center

NYU Langone Medical Center, a world-class, patient-centered, integrated academic medical center, is one of the nation’s premier centers for excellence in clinical care, biomedical research, and medical education. Located in the heart of Manhattan, NYU Langone is composed of four hospitals—Tisch Hospital, its flagship acute care facility; Rusk Rehabilitation; the Hospital for Joint Diseases, the Medical Center’s dedicated inpatient orthopaedic hospital; and Hassenfeld Children’s Hospital, a comprehensive pediatric hospital supporting a full array of children’s health services across the Medical Center—plus the NYU School of Medicine, which since 1841 has trained thousands of physicians and scientists who have helped to shape the course of medical history. The Medical Center’s tri-fold mission to serve, teach, and discover is achieved 365 days a year through the seamless integration of a culture devoted to excellence in patient care, education, and research.

About New York University College of Nursing

NYU College of Nursing is a global leader in nursing education, research, and practice. It offers a Bachelor of Science in Nursing, a Master of Science and Post-Master’s Certificate Programs, a Doctor of Philosophy in Research Theory and Development, and a Doctor of Nursing Practice degree.


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