MARIJUANA LINKED TO BRAIN PROBLEMS

CHICAGO, Illinois (Reuters) -- Heavy, chronic marijuana users suffer
memory loss and attention problems that can affect their work,
learning and life, researchers reported on Tuesday.

But in an indication of the controversy surrounding a drug said to be
used at least weekly by 7 million people in the United States, a
medical expert not involved in the study questioned the findings and
whether the alleged adverse impact of the drug persists.

The study was published in this week's Journal of the American Medical
Association. It was based on patients seeking help for marijuana
dependence at clinics in Seattle, Farmington, Connecticut, and Miami,
between 1997 and 2000.

The study examined 51 people who had been using marijuana regularly
for an average of 24 years, 51 short-term users and 33 nonusers who
were included as controls for comparison purposes in the research.

"Long-term users ... performed significantly less well on tests of
memory and attention than nonuser controls and shorter-term users with
a mean of 10 years' use," the study said.

On one verbal learning test "long-term users recalled significantly
fewer words than either shorter-term users or controls; there was no
difference between shorter-term users and controls. Long-term users
showed impaired learning, retention and retrieval compared with
controls," it added.

The authors of the study, Nadia Solowij at the University of New South
Wales, Sydney, Australia, and colleagues with the Marijuana Treatment
Project Research Group said their study confirmed and extended
previous findings of cognitive impairments among chronic heavy
marijuana users.

"For habitual users, the kinds of impairments observed in this study
have the potential to impact academic achievements, occupational
proficiency, interpersonal relationships and daily functioning," the
study concluded.

But in an editorial published in the same issue, Harrison Pope of
Harvard Medical School said "a recent meta-analysis of
neuropsychological studies of long-term marijuana users found no
significant evidence for deficits in seven of eight ... ability areas
and only a small effect size for the remaining area of learning."

In a separate statement he said the study does not explore whether the
heavy users might have been taking other drugs that might have
accounted for the deficits uncovered, or whether they might have been
suffering from anxiety or depression that could cause the problems
noted.

"Another recent study from our laboratory ... found virtually no
significant differences between 108 heavy cannabis users and 72
controls -- screened to exclude those with current psychiatric
disorders, medication use, or any history of significant use of other
drugs or alcohol -- on a battery of ten neuropsychological tests after
28 days of supervised abstinence from the drug," he said.

Pope, who directs the Biological Psychiatry Laboratory at McLean
Hospital in Belmont, Massachusetts, added: "The safest thing to say at
this point is that the jury is still out on the question of whether
long-term marijuana use causes lasting impairment in brain function."

[NOTE: Below is the abstract of the report from the JAMA website
http://jama.ama-assn.org/ ]

COGNITIVE FUNCTIONING OF LONG-TERM HEAVY CANNABIS USERS SEEKING TREATMENT

Nadia Solowij, PhD; Robert S. Stephens, PhD; Roger A. Roffman, DSW; Thomas
Babor, PhD, MPH; Ronald Kadden, PhD; Michael Miller, PhD; Kenneth
Christiansen, PsyD; Bonnie McRee, MPH; Janice Vendetti, MPH; for the
Marijuana Treatment Project Research Group

Context

Cognitive impairments are associated with long-term cannabis use, but the
parameters of use that contribute to impairments and the nature and
endurance of cognitive dysfunction remain uncertain.

Objective

To examine the effects of duration of cannabis use on specific areas of
cognitive functioning among users seeking treatment for cannabis dependence.

Design, Setting, and Participants

Multisite retrospective cross-sectional neuropsychological study conducted
in the United States (Seattle, Wash; Farmington, Conn; and Miami, Fla)
between 1997 and 2000 among 102 near-daily cannabis users (51 long-term
users: mean, 23.9 years of use; 51 shorter-term users: mean, 10.2 years of
use) compared with 33 nonuser controls.

Main Outcome Measures

Measures from 9 standard neuropsychological tests that assessed attention,
memory, and executive functioning, and were administered prior to entry to
a treatment program and following a median 17-hour abstinence.

Results

Long-term cannabis users performed significantly less well than
shorter-term users and controls on tests of memory and attention. On the
Rey Auditory Verbal Learning Test, long-term users recalled significantly
fewer words than either shorter-term users (P = .001) or controls (P =
.005); there was no difference between shorter-term users and controls.
Long-term users showed impaired learning (P = .007), retention (P = .003),
and retrieval (P = .002) compared with controls. Both user groups performed
poorly on a time estimation task (P<.001 vs controls). Performance measures
often correlated significantly with the duration of cannabis use, being
worse with increasing years of use, but were unrelated to withdrawal
symptoms and persisted after controlling for recent cannabis use and other
drug use.

Conclusions

These results confirm that long-term heavy cannabis users show impairments
in memory and attention that endure beyond the period of intoxication and
worsen with increasing years of regular cannabis use.

JAMA. 2002;287:1123-1131

Author Affiliations: National Drug and Alcohol Research Centre, University
of New South Wales, Sydney, and Department of Psychology, University of
Wollongong, Wollongong (Dr Solowij), New South Wales, Australia; Department
of Psychology, Virginia Polytechnic Institute and State University,
Blacksburg, Va (Dr Stephens); Innovative Programs Research Group, School of
Social Work, University of Washington, Seattle (Dr Roffman); Department of
Community Medicine (Dr Babor and Mss McRee and Vendetti) and Department of
Psychiatry (Dr Kadden), University of Connecticut Health Center,
Farmington; and The Village South Inc, Miami, Fla (Drs Miller and
Christiansen).

Corresponding Author and Reprints: Nadia Solowij, PhD, National Drug and
Alcohol Research Centre, University of New South Wales, Sydney, NSW 2052,
Australia (e-mail: n.solowij@unsw.edu.au).

Author Contributions:

Study concept and design: Solowij, Stephens, Roffman.

Acquisition of data: Stephens, Roffman, Kadden, Miller, Christiansen,
McRee, Vendetti.

Analysis and interpretation of data: Solowij, Stephens.

Drafting of the manuscript: Solowij.

Critical revision of the manuscript for important intellectual content:
Solowij, Stephens, Roffman, Babor, Kadden, Miller, Christiansen, McRee,
Vendetti.

Statistical expertise: Solowij, Stephens.

Obtained funding: Solowij, Stephens, Roffman, Babor, Kadden, Miller.

Administrative, technical, or material support: Solowij, Roffman, McRee,
Vendetti.

Study supervision: Solowij, Stephens, Roffman, Babor, Kadden, Miller,
Christiansen, McRee, Vendetti.

Other Members of the Marijuana Treatment Project Research Group include
Kathleen Carroll, PhD, Karen Steinberg, PhD, (Coordinating Center,
University of Connecticut Health Center, Department of Community Medicine),
Mark Litt, PhD (Farmington Clinical Research Unit, University of
Connecticut Health Center, Department of Psychiatry), Jean Donaldson, MA,
and James Herrell, PhD (Center for Substance Abuse Treatment).

Funding/Support: This study was conducted as part of the Marijuana
Treatment Project, a Cooperative Agreement for a multisite study of the
effectiveness of brief treatment for cannabis dependence. It was funded by
the Substance Abuse and Mental Health Services Administration, Center for
Substance Abuse Treatment (CSAT), US Department of Health and Human
Services (grants UR4 TI11270, UR4 TI11273, UR4 TI11274, UR4TI11310). The
research was conducted in Farmington, Conn, Miami, Fla, and Seattle, Wash,
in cooperation with the following institutions: University of Connecticut
Health Center, The Village South Inc, University of Washington, and
Evergreen Treatment Services.

Acknowledgment: We are grateful to Aimee Balmer-Campbell, BA, Kara Brennan
Dion, BA, David Duresky, MA, Dave Ghany, BA, Brian Glidden, BA, Cara
Gluskoter, MS, Cher Gunby, BA, Jennifer Haley, BA, Heather Haynes, RN,
Patricia Holkon, MA, Elise Kabella, PhD, Priscilla Morse, MA, Joe Picciano,
MS, Sam Schwartz, MSW, Megan Swan, MA, Debbie Talamini, AS, and Anna Wolfe,
BA, for input and assistance with data collection and trial management,
Peter Caputi, BA, GradDip, for statistical advice, Brin Grenyer, PhD, for
comments on the manuscript, Eva Congreve, DipLib, for library assistance,
and to all participants in this research.