Harvard Scientists Studied the Brains of Pot Smokers, and the Results Don’t Look Good


Harvard Scientists Studied the Brains of Pot Smokers, and the Results Don’t Look Good

The news: Every day, the push toward national legalization of marijuana seems more and more inevitable. As more and more politicians and noted individuals come out in favor of legalizing or at least decriminalizing different amounts of pot, the mainstream acceptance of the recreational use of the drug seems like a bygone conclusion. But before we can talk about legalization, have we fully understood the health effects of marijuana?

According to a new study published in the Journal of Neuroscience, researchers from Harvard and Northwestern studied the brains of 18- to 25-year-olds, half of whom smoked pot recreationally and half of whom didn’t. What they found was rather shocking: Even those who only smoked few times a week had significant brain abnormalities in the areas that control emotion and motivation.

“There is this general perspective out there that using marijuana recreationally is not a problem — that it is a safe drug,” said Anne Blood, a co-author of the study. “We are seeing that this is not the case.”

The science: Similar studies have found a correlation between heavy pot use and brain abnormalities, but this is the first study that has found the same link with recreational users. The 20 people in the “marijuana group” of the study smoked four times a week on average; seven only smoked once a week. Those in the control group did not smoke at all.

“We looked specifically at people who have no adverse impacts from marijuana — no problems with work, school, the law, relationships, no addiction issues,” said Hans Breiter, another co-author of the study.

Using three different neuroimaging techniques, researchers then looked at the nucleus accumbens and the amygdala of the participants. These areas are responsible for gauging the benefit or loss of doing certain things, and providing feelings of reward for pleasurable activities such as food, sex and social interactions.

“This is a part of the brain that you absolutely never ever want to touch,” said Breiter. “I don’t want to say that these are magical parts of the brain — they are all important. But these are fundamental in terms of what people find pleasurable in the world and assessing that against the bad things.”

Shockingly, every single person in the marijuana group, including those who only smoked once a week, had noticeable abnormalities, with the nucleus accumbens and the amygdala showing changes in density, volume and shape. Those who smoked more had more significant variations.

What will happen next? The study’s co-authors admit that their sample size was small. Their plan now is to conduct a bigger study that not only looks at the brain abnormalities, but also relates them to functional outcomes. That would be a major and important step in this science because, as of now, the research indicates that marijuana use may cause alterations to the brain, but it’s unclear what that might actually mean for users and their brains.

But for now, they are standing behind their findings.

“People think a little marijuana shouldn’t cause a problem if someone is doing OK with work or school,” said Breiter. “Our data directly says this is not so.”



By Imad Bayoun

In the Name of Allah, Ar-Rahman, Ar-Raheem

The issue of legalizing marijuana consumption has been circulating for a while, with people on both sides passionately defending their views.

Marijuana is the most common illicit drug used in the United States. After a period of decline in the last decade, its use has generally increased among young people since 2007, corresponding to a diminishing perception of the drug’s risks. More teenagers are now current smokers of marijuana than of cigarettes (1).

Marijuana is a dry, shredded green and brown mix of leaves, flowers, stems, and seeds from the hemp plant Cannabis sativa. In a more concentrated, resinous form, it is called hashish (1). Two other common Cannabis species are Cannabis indica and Cannabis ruderalis. All three Cannabis species are members of the botanical family Cannabaceae, known to contain cannabinoids, a group of chemicals which produce mental and physical effects when consumed.

Cannabinoids are closely related to substances produced naturally by the human brain, called endogenous cannabinoids or endocannabinoids, that play an important role in controlling pain, memory, neurodegeneration, and in inflammation (2). Marijuana intake results in increased level of cannabinoids in the body, altering moods and resulting in different effects. Proponents of legalizing the use of marijuana contend that it helps decreasing pain and alleviating depression. But as is the case of mood-altering chemicals, there are side and direct effects of taking marijuana. The effects differ from one person to another and based on the amount taken.

Effects of marijuana consumption:

Two reports by the “National Institute of Drug Abuse” (1) and the “National Criminal Justice Reference Service” (3) summarize some of the effects of marijuana consumption. Some of the reported short-term effects include:

Distorted perception (sights, sounds, time, touch)
Problems with memory and learning
Loss of coordination
Trouble with thinking and problem-solving
Increased heart rate, reduced blood pressure
Anxiety, fear, distrust, or panic.
More frequent acute chest illnesses
Increased risk of lung infections
Under high dosage: Hallucinations, delusions, impaired memory, disorientation
It was also found that the observed declines of cognitive functions (concentration, memory, learning, executive functioning, …) seem to be irreversible with persistent marijuana users. This was particularly significant in adolescents, who have rapidly developing brains (4).

Furthermore, there is evidence that the use of marijuana is associated with an earlier onset of psychosis, and earlier age of hospital admissions to treat psychosis (5, 6). Marijuana can even be an independent factor in itself in developing psychosis (7).

Marijuana was also found to contain more carcinogenic hydrocarbons than tobacco (8). And though most marijuana smokers consume a lot less cannabis than cigarette smokers consume tobacco, marijuana smokers typically inhale deeper and hold the smoke in their lungs longer than tobacco smokers. As such, their lungs are exposed to those carcinogens longer, and the harmful effects of smoking marijuana should not be ignored.

It should be noted also that while marijuana use may not be physiologically addictive, it can still be psychologically addictive. Marijuana users often resort to using the weed to cope with their distress and life problems.

The Islamic Concern:

With the “marijuana debate” commonly focusing on its legalization, of more concern to the Muslims is the Islamic legitimacy of consuming it, whether Halal or Haram.

It should first be clarified that Legalizing and Islamic permissiveness are two completely separate issues. Legalization is not a Shar`ee Fatwa. Even if the state/government decided to make marijuana consumption legal, it does not mean that it is Islamically permissible, i.e. Halal. Alcohol is legal, yet clearly established to be Haram.

Also, it should be indicated that though there might be some established reports of benefit from marijuana consumption, that itself cannot be a basis for Islamic permissiveness. There are actual reports of benefits from wine consumption, and they are recognized in the Quran; yet wine is still prohibited. Surat Al-Baqarah, verse 219 states:

يَسْأَلُونَكَ عَنِ الْخَمْرِ وَالْمَيْسِرِ قُلْ فِيهِمَا إِثْمٌ كَبِيرٌ وَمَنَافِعُ لِلنَّاسِ وَإِثْمُهُمَآ أَكْبَرُ مِن نَّفْعِهِمَا

They ask thee concerning wine and gambling; say: “In them is great sin, and some profit, for men; but the sin is greater than the profit.

So the deciding consideration here is the overall effects of wine and gambling, and not just some partial benefits.

Another important clarification is that for us to conclude that marijuana is prohibited (or permissible), it does not need to be prohibited directly by name, in either a Quranic verse or a Prophetic narration (Hadeeth). The Islamic Shari`ah does not, and could not, include neither all prohibitions nor all permissions. The Shari`ah sometimes gives specific, but mostly general guidelines that accommodate all ensuing situations. The Prophet (S) did not list all animal species that are prohibited to eat, rather he mentioned some general categories, such carnivorous animals.

Now concerning general prohibitions, Allah (S) indicates in Surat Al-A`raaf, verse 157, that the duty of the Prophet (S) is to prohibit anything harmful:

يَأْمُرُهُمْ بِالْمَعْرُوفِ وَيَنْهَاهُمْ عَنِ الْمُنْكَرِ وَيُحِلُّ لَهُمُ الطَّيِّبَاتِ وَيُحَرِّمُ عَلَيْهِمُ الْخَبَائِثَ

… he commands them what is just and forbids them what is evil; he allows them as lawful what is good (and pure) and prohibits them from what is bad (and impure)

The same was repeated in the famous Hadeeth narrated in Imam Malik’s Muwatta’, where the Prophet (S) said:

لا ضرر ولا ضرار

There shall be no harm, nor harming.

Thus, the harm is to be removed; and anything established to be harmful (medically and otherwise) would go under this rule, and becomes prohibited, Islamically.

Furthermore, one of the main five purposes of the Islamic Shari`ah is to preserve the human mind. Thus, anything that harms the mind goes under the prohibition, as indicated in the Hadeeth narrated in Sahih Muslim:

كل مسكر خمر ، وكل مسكر حرام ، ومن شرب الخمر في الدنيا فمات وهو يدمنها لم يتب لم يشربها في الآخرة

Anything that leads to drunkiness is Khamr (wine), and all wine is prohibited. And whoever drinks wine in this life and dies while still a wine-drinker before repenting, will not drink it in the Herafter.

“Khamr”, commonly translated as “wine” or “alcohol”, is more generally defined as anything that conceals the mind, and not just as wine, as in the Hadeeth narrated by Ibn Omar in both Bukhari and Muslim:

سمعت عمر رضي الله عنه على منبر النبي صلى الله عليه وسلم يقول : ( أما بعد ، أيها الناس ، إنه نزل تحريم الخمر وهي من خمسة : من العنب والتمر والعسل والحنطة والشعير ، والخمر ما خامر العقل )

I heard Omar (R) on the pulpit of the Prophet (S) saying: “Indeed people, the prohibition of khamr was revealed; and it can be made from five (not only): grapes, dates, honey, grains, and barley. And ‘Khamr’ is that which conceals the mind.”

More directly, a Hadeeth narrated in Imams Ahmad’s and Abu Dawood’s, stated:

ونهى صلى الله عليه وسلم عن كل مسكر وكل مفتر

The Prophet (S) prohibited every substance that causes drunkiness or that is a “mufter.”

And Al-Khatabi said:

قَالَ الْخَطَّابِيُّ : الْمُفْتِر كُلّ شَرَاب يُورِث الْفُتُور وَالرَّخْوَة فِي الأَعْضَاء وَالْخَدَرَ فِي الأَطْرَاف وَهُوَ مُقَدِّمَة السُّكْر , وَنَهَى عَنْ شُرْبه لِئَلا يَكُون ذَرِيعَة إِلَى السُّكْر .

A “mufter” is any drink that causes excessive relaxation in the limbs, and it normally happens before drunkiness; and it was prohibited so as not to make it acceptable to get drunk.

Thus, it does not have to lead into a state of drunkiness, or complete concealment of the mind, for it to be prohibited. Even if it leads to the above-described state of relaxation it might still be prohibited by the Prophet.

Though any of the above arguments might be sufficient basis for the prohibition, based on all of the above, the scholars have concluded that Cannabis/marijuana consumption is prohibited in Islam, i.e., Haram. It’s harmful effects have been established, and it is clearly categorized as at least bad/impure (خبيث), harmful (ضار); and depending on the person, it causes excessive relaxation (مفتر), and under high doses, causes a state similar to drunkiness (مسكر).

Islamic Permissibility:

Using Cannabis/marijuana, like other prohibitions, can be Islamically permissible under certain situations, based on the Shar`ee rule “the necessities legitimizes the prohibitions.”

The rule was derived from several verses and Ahadeeth, as in the following:

Surat Al-An`aam, verse 145:

فَمَنِ اضْطُرَّ غَيْرَ بَاغٍ وَلا عَادٍ فَإِنَّ رَبَّكَ غَفُورٌ رَحِيمٌ

… But if a person is forced by necessity, without willful disobedience, nor transgressing due limits, your Lord is Oft-forgiving, Most Merciful

Surat Al-Baqarah, verse 173:

فَمَنِ اضْطُرَّ غَيْرَ بَاغٍ وَلا عَادٍ فَلا إِثْمَ عَلَيْهِ إِنَّ اللَّهَ غَفُورٌ رَحِيمٌ

…But if one is forced by necessity, without willful disobedience, nor transgressing due limits, then is he guiltless; for Allah is Oft-forgiving Most Merciful

Surat Al-Ma’edah, verse 6:

مَا يُرِيدُ اللَّهُ لِيَجْعَلَ عَلَيْكُمْ مِنْ حَرَجٍ وَلَكِنْ يُرِيدُ لِيُطَهِّرَكُمْ

Allah does not wish to place you in a difficulty, but to make you pure, and to complete His favor to you, that ye may be grateful.

Hence, Imams An-Nawawi in “Rawdat At-Talibeen”, Al-Mawardi in “Al-Insaaf”, Ibn Farhon Al-Maliki in “Tabsirat Al-Ahkam”, and others consider using a drug for anesthesia for surgical purposes (for example) legitimate.

Nevertheless, there is a fine line between Halal and Haram, and there are essential controlling guidelines for applying the “rule of necessity”:

The necessity has to be real, where there is a fear of a real harm.
The use of the prohibited substance should result in a real benefit, either directly or protecting against a real harm. And this benefit should be established by a credible expert, a physician in this case. It cannot be decided by the person himself, which can be very dangerous, yet is very common. Several young brothers research it themselves, and give themselves the credibility to decide what is good or bad for them, from the medical perspective. This becomes very tempting, especially with the widespread Readers Digest types of reports. Such reports give one the illusion of being really knowledgeable. Furthermore most of these reports have not been reviewed scientifically, and even if they have, still require an expert to implement them in the proper way.
Another related problem here is many of the brothers who start consuming marijuana at a very early age, do so simply based on a suggestion from a friend that “knows.” It is very common for youth to use their peers as sources of information. Then some of these brothers themselves spread it further in the same way it reached them. I seriously caution my dear brothers and sisters not to rush into giving a “fatwa” about something that significant. No one wants to bear the burden of their own sins, as well as those of others.

The expected benefit cannot be achieved by other, legitimate means. If there are other means to achieve the same benefit, then marijuana remains prohibited.
The use of the prohibited means should not lead to a bigger harm.
The permission is limited only to the period needed time to achieve the sought benefit. Thus, it is temporary, and once the need is gone, marijuana consumption goes back to the original state, which is the prohibition.
The permission is limited only to the amount needed to achieve the benefit not more. It is not an open permission to use it as often and as much as one desires.
For my brothers and sisters that got into consuming Cannabis in any form, I suggest returning to Allah (S) with repentance, indeed Allah is the All-Forgiving, All-Merciful. It is also be essential to change the environment (whether friends or places) that encourages marijuana consumption. There might also be a need to consult with a physician, explaining the situation, and asking for help.

I pray for Allah (S) to keep us firm on His path, in this life and the Next.

I ask Allah (S) to reward my dear brothers, Drs. Khaled Bahajri, MD/PhD, and Othman Muhammad, MD; for reviewing the article and providing valuable feedback and additions.


1. “DrugFacts: Marijuana”, a report by Report by the National Institute of Drug Abuse


2. Roger A. Nicoll & Bradley E. Alger. The Brain’s Own Marijuana. Scientific American, Nov. 2004.

3. “Marijuana, Myths & Facts”, a document put forth by the National Criminal Justice Reference Service:


4. Meier MH, Caspi A, Ambler A, Harrington H, Houts R, Keefe RS, McDonald K, Ward A, Poulton R, Moffitt TE. Persistent cannabis users show neuropsychological decline from childhood to midlife. PubMed, 2012: www.ncbi.nlm.nih.gov/pubmed/22927402).

5. Galvez-Buccollini JA, Proal AC, Tomaselli V, Trachtenberg M, Coconcea C, Chun J, Manschreck T, Fleming J, Delisi LE. Association between age at onset of psychosis and age at onset of cannabis use in non-affective psychosis. PubMed, 2012: www.ncbi.nlm.nih.gov/pubmed?term=juan buccollini galvez)

6. Large M, Sharma S, Compton MT, Slade T, Nielssen O. Cannabis Use and Earlier Onset of Psychosis, A Systematic Meta-analysis. JAMA Psychiatry, 2011 (6): archpsyc.jamanetwork.com/data/Journals/PSYCH/5318/yma05005_555_561.pdf

7. Le Bec PY, Fatséas M, Denis C, Lavie E, Auriacombe M. Cannabis and psychosis: search of a causal link through a critical and systematic review. PubMed, 2009: www.ncbi.nlm.nih.gov/pubmed/19748375)

8. Gideon A. Caplan GA & Brigham BA. Marijuana Smoking and Carcinoma