I suppose it's time to pull out the peer-reviewed journal articles related to the use of marijuana. Sorry to burst your bubbles, but I take higher credence in peer-reviewed stuff.
1) Title: Altered brain tissue composition in heavy marijuana users.
Author(s): Matochik JA; Eldreth DA; Cadet J; Bolla KI
Source: Drug and Alcohol Dependence (DRUG ALCOHOL DEPENDENCE), 2005 Jan 7; 77(1): 23-30 (39 ref)
Abstract: Marijuana is the most widely used illicit substance in the United States; however, previous imaging studies have not detected altered brain structure in marijuana users compared to non-users. Voxel-based morphometry was used to investigate possible differences in brain tissue composition in a group of 11 heavy marijuana users and a group of 8 non-users. All participants were male. Statistical comparisons were made at the voxel level on T1-weighted magnetic resonance images to determine differences in gray matter and white matter tissue density. Compared to non-users, marijuana users had lower gray matter density in a cluster of voxels in the right parahippocampal gyrus (P = 0.0001), and greater density bilaterally near the precentral gyrus and the right thalamus (P < 0.04). Marijuana users also had lower white matter density in the left parietal lobe (P = 0.03), and higher density around the parahippocampal and fusiform gyri on the left side compared to non-users (P < 0.002). Longer duration of marijuana use (in years) was significantly correlated with higher white matter tissue density in the left precentral gyrus (P = 0.045). Our preliminary results suggest evidence of possible structural differences in the brain of heavy marijuana users, and localize regions for further investigation of the effects of marijuana in the brain.
2) Title: Dose-related neurocognitive effects of marijuana use.
Author(s): Bolla KI; Brown K; Eldreth D; Tate K; Cadet JL
Source: Neurology (NEUROLOGY), 2002 Nov 12; 59(9): 1337-43 (43 ref)
Abstract: BACKGROUND: Although about 7 million people in the US population use marijuana at least weekly, there is a paucity of scientific data on persistent neurocognitive effects of marijuana use. OBJECTIVE: To determine if neurocognitive deficits persist in 28-day abstinent heavy marijuana users and if these deficits are dose-related to the number of marijuana joints smoked per week. METHODS: A battery of neurocognitive tests was given to 28-day abstinent heavy marijuana abusers. RESULTS: As joints smoked per week increased, performance decreased on tests measuring memory, executive functioning, psychomotor speed, and manual dexterity. When dividing the group into light, middle, and heavy user groups, the heavy group performed significantly below the light group on 5 of 35 measures and the size of the effect ranged from 3.00 to 4.20 SD units. Duration of use had little effect on neurocognitive performance. CONCLUSIONS: Very heavy use of marijuana is associated with persistent decrements in neurocognitive performance even after 28 days of abstinence. It is unclear if these decrements will resolve with continued abstinence or become progressively worse with continued heavy marijuana use.
3)Title: Neurocognitive performance of methamphetamine users discordant for history of marijuana exposure.
Author(s): Gonzalez R; Rippeth JD; Carey CL; Heaton RK; Moore DJ; Schweinsburg BC; Cherner M; Grant I
Source: Drug and Alcohol Dependence (DRUG ALCOHOL DEPENDENCE), 2004 Nov 11; 76(2): 181-90 (69 ref)
Abstract: Abuse of the stimulant drug methamphetamine is associated with neural injury and neuropsychological (NP) deficits, while the residual effects of marijuana use remain uncertain. We sought to determine if methamphetamine dependent persons who also met criteria for marijuana abuse or dependence evidenced different NP performance than those with dependence for methamphetamine alone. We examined three groups that did not differ significantly on important demographic factors: (1) subjects with a history of methamphetamine dependence and history of marijuana abuse/dependence (METH+/MJ+, n=27); (2) methamphetamine dependent subjects without history of marijuana abuse/dependence (METH+/MJ-, n=26); (3) a control group with minimal or no drug use (n=41). A comprehensive NP battery was administered and performance was quantified for five cognitive ability areas. The METH+/MJ- group generally demonstrated the greatest NP impairment, with statistically significant differences observed between the METH+/MJ- and control group in learning, retention/retrieval, and a summary score of global NP performance. The METH+/MJ+ group did not differ significantly from the control or METH+/MJ- group on any NP ability. However, there was a significant linear trend in the global NP score suggesting that the METH+/MJ+ performed intermediate to the control and METH+/MJ- groups. Based on these findings, we cannot conclude that there is a protective effect of marijuana use in methamphetamine users; however, marijuana use clearly did not appear to exacerbate methamphetamine neurotoxicity. Further investigations are needed to determine if the emerging literature, suggesting that certain cannabinoids might have neuroprotective actions, is generalizable to community-dwelling substance abusers.
4) Title: Marijuana and cannabinoids: effects on infections, immunity, and AIDS.
Author(s): Cabral GA
Source: Journal of Cannabis Therapeutics (J CANNABIS THER), 2001; 1(3/4): 61-85
Abstract: Marijuana and its major psychoactive component, delta-9-tetrahydrocannabinol (THC), alter resistance to bacterial, protozoan, and viral infections in vivo and in vitro. These alterations have been accompanied by modifications in functional components of the immune system. In addition, marijuana and THC, as well as other cannabinoids, have been reported to directly affect functional activities of lymphocytes, macrophages, natural killer cells, and other immunocytes. These include effects on cytokine production resulting in a shift in the balance of Th1 versus Th2 cytokines. Both receptor and non-receptor mediated modes of action have been proposed as causative of cannabinoid effects. Reports that marijuana and THC alter anti-microbial activity in vivo arid in vitro indicate that its use presents a potential risk of decreased resistance to infections. However, few controlled longitudinal epidemiological and immunological studies have been undertaken to correlate the immunosuppressive effects of marijuana smoke or cannabinoids on the incidence of' infections or disease in humans.
I didn't want to fill up the whole page with abstracts and such, but if you want I have plenty more where that came from.