Correlation, causation, and association – What does it all mean???

A comment posted by a reader on a post reprimanded me for suggesting that marijuana caused relationships to go bad.

In this instance the reader was mistaken, as I had specifically used the word “associated”, but the comment made me think that maybe I should explain the differences between correlation, causation, and association. I’m a scientist studying addiction, and in the field, it’s very important to be clear about what each of the words you use means.

Being clear about inferences in research

Correlation – When researchers find a correlation, which can also be called an association, what they are saying is that they found a relationship between two, or more, variables. For instance, in the case of the marijuana post, the researchers found an association between using marijuana as a teen, and having more troublesome relationships in mid, to late, twenties.

Correlations can be positive – so that as one variable (marijuana smoking) goes up, so does the other (relationship trouble); or they can be negative, which would mean that as one variable goes up (methamphetamine smoking) another goes down (grade point average).

The trouble is that, unless they are properly controlled for, there could be other variables affecting this relationship that the researchers don’t know about. For instance, education, gender, and mental health issues could be behind the marijuana-relationship association (these variables were all controlled for by the researchers in that study). Researchers have at their disposal a number of sophisticated statistical tools to control for these, ranging from the relatively simple (like multiple regression) to the highly complex and involved (multi-level modeling and structural equation modeling). These methods allow researchers to separate the effect of one variable from others, thereby leaving them more confident in making assertions about the true nature of the relationships they found. Still, even under the best analysis circumstances, correlation is not the same as causation.

Causation – When an article says that causation was found, this means that the researchers found that changes in one variable they measured directly caused changes in the other. An example would be research showing that jumping of a cliff directly causes great physical damage. In order to do this, researchers would need to assign people to jump off a cliff (versus lets say jumping off of a 12 inch ledge) and measure the amount of physical damage caused. When they find that jumping off the cliff causes more damage, they can assert causality. Good luck recruiting for that study!

Most of the research you read about indicates a correlation between variables, not causation. You can find the key words by carefully reading. If the article says something like “men were found to have,” or “women were more likely to,” they’re talking about associations, not causation.

Why the correlation-causation difference?

The reason is that in order to actually be able to claim causation, the researchers have to split the participants into different groups, and randomly assign some to the behavior or condition they want to study (like taking a new drug), while the rest receive something else. This is in fact what happens in clinical trials of medication because the FDA requires proof that the medication actually makes people better (more so than a placebo). It’s this random assignment to conditions (or randomization) that makes experiments suitable for the discovery of causality. Unlike in association studies, random assignment assures (if everything is designed correctly) that its the behavior being studied, and not some other random effect, that is causing the outcome.

Obviously, it is much more difficult to prove causation than it is to prove an association.

Should we just ignore associations?

No! Not at all!!! Not even close!!! Correlations are crucial for research and still need to be looked at and studied, especially in some areas of research like addiction.

The reason is simple – We can’t randomly give people drugs like methamphetamine as children and study their brain development to see how the stuff affects them, that would be unethical. So what we’re left with is a the study of what meth use (and use of other drugs) is associated with. It’s for this reason that researchers use special statistical methods to assess associations, making certain that they are also considering other things that may be interfering with their results.

In the case of the marijuana article, the researchers ruled out a number of other interfering variables known to affect relationships, like aggression, gender, education, closeness with other family members, etc. By doing so, they did their best to assure that the association found between marijuana and relationship status was real. Obviously other possibilities exist, but as more researchers assess this relationship in different ways, we’ll learn more about its true nature.

This is how research works.

It’s also how we found out that smoking causes cancer. Through endlessly repeated findings showing an association. That turned out pretty well, I think…

Shame on me – Stigma and addiction in treatment

I keep hearing that back in the old days of addiction treatment, shame was the main motivating factor used by rehab counselors. Everyone admits that it proved to be a horrible motivator. It simply didn’t work! With all the advances in research into addiction, that must have changed, right?

I don’t think so. I see shame and stigma every time I hear an addict talk about their drug use. The shame is there in their eyes as they tell the stories of their trouble and the struggles of their recovery. Given the low rates of success in addiction treatment, the shame rests firmly in the inability to quit as well. A relapse is often seen as the ultimately shameful experience for an addict. The stigma of addicts as hopeless is rampant.

Still, we have evidence of genetic predisposition to drug abuse and addiction, we know of environmental factors that make it more likely that people will get hooked. The effect of many drugs on the brain make unsuspecting lab animals as likely to become addicted as any one of us and I’m pretty sure that shame doesn’t play a role in their process.

With all this evidence, why is the stigma of drug addicts still around? Why are they the only ones being blamed for their condition?

The evidence I cited isn’t that different from that known for cancer, yet we scarcely blame cancer patients for their disease. Even in the case of smokers who become ill, their is still sympathy for their suffering. So why are addicts different?

There are good addiction treatment options out there, as long as we don’t give up on the person and simply view their addiction as evidence of their weak character. Given the changes that long term drug use produces in the brain, it’s a miracle anyone recovers at all. We should be grateful for that.

Tobacco smoking alone isn’t enough: More than smoking important in lung cancer death

Christopher Russell and Adi Jaffe

The tobacco epidemic already kills 5.4 million people a year from lung cancer, heart disease and other illnesses. By 2030, the death toll will exceed eight million a year. Unless urgent action is taken tobacco could kill one billion people during this century. (The World Health Organization Report on the Global Tobacco Epidemic, 2008)

These are some scary numbers, right? Cigarette smoking, according to the WHO, is the single most preventable cause of death in the world today, and in conveying these deadly statistics to the general public, cigarettes have come to be alternatively referred to by smokers and non-smokers as “cancer sticks”, “nicotine bullets”, and “coffin nails”.

But does smoking really ‘kill’ anybody in the literal sense with which we use this word?  To an epidemiologist, tobacco smoking (nor many other drugs of abuse for that matter) does not “kill” a person or “cause” illness or death in the way the words “kill” and “cause” are typically understood by the media and general public. For example, if I shoot someone in the head, stab another in the heart, and strangle a third till he stops breathing, it is reasonable to say that my actions were the direct, sole, and sufficient causes of death – I would have killed them. Smoking, however, is often neither a sole nor sufficient ‘cause’ of lung cancer, coronary heart disease, or myocardial infarction because non-smokers die from these diseases, and for example, because only 1 in 10 heavy smokers die from lung cancer when one looks at the overall numbers. Continue reading “Tobacco smoking alone isn’t enough: More than smoking important in lung cancer death”

About Addiction: Smoking, Drugs, Drinking and Cancer

New links for interesting articles about addiction. Check them out!

Tobacco, nicotine, and Smoking

Medical News Today: According to a recent study in China there is a new effective strategy for treating tobacco addiction.  Researchers have developed a novel tea filter that seems to help with cigarette addiction. (Note: this link doesn’t give direct access to the article so we’re basing the summary on the article itself)

SAMHSA: According to a new nationwide study, adolescent smoking may be influenced by mothers’ smoking or depression. The study states that adolescents living with mothers who smoke are 25.6% more likely to smoke. It’s frightening to think that 1.4 million 11-17 year old kids started smoking in the past 12 months!

Science Daily: Exposure to prenatal smoking may lead to psychiatric problems. According to new research, exposure to prenatal smoking can increase the need for psychotropic medications in childhood and young adulthood.

Hard drugs

Science Daily:  A newly developed and tested modified enzyme has been shown to break down cocaine into inactive products nearly 1000 times faster than the human body. The article states further that cocaine toxicity due to drug overdose results in more than half a million emergency room visits annually. This new enzyme could help prevent OD deaths by breaking down the drug.

Fox News: The number of soldiers seeking opiate abuse treatment has been increasing, going up from 89 in 2004 to 529 last year.

Addiction Inbox: A study that uses the Stroop test (have to name the colors of words and not the words themselves) seems to be a good predictor for addiction treatment effectiveness and drop out rates. Pretty cool stuff!

Alcohol

Join Together: This is a short article summarizing research which shows that rare childhood leukemia is tied to drinking during pregnancy. According to this research, children whose mothers are drinking during pregnancy are 56 percent more likely to develop a rear form of leukemia called AML.

Addiction Tomorrow: Britain is considering raising the prices of their very low-end alcohols most likely in an attempt to damper the young adults that binge drink and of alcoholics since they are most often the ones that drink the low-end alcohol.

About Addiction: Alcohol, breast cancer & war veterans

Check out our weekly links about addiction!

Health Day: A new study shows that breast cancer survivors who smoke are at increased risk for a second cancer. The time frame to develop second cancer is fifteen years.

Cesar Fax: Drug positives increase consistently with age amongst DC juvenile arrestees. 53% of the juvenile arrestees tested positive for drugs.

Psychology Today: An article from Psychology Today (which Adi has been writing for so check them out!) and discusses the issue of war veterans and drug use as well as PTSD. It relates the discussion to soldiers in Iraq and Afghanistan.

Science Daily: There are some new insights into how alcohol affects brain function. Drinking alcohol over a long period of time does profoundly affect the brain.

Science Daily: More about alcohol! According to Science Daily, genetic differences that make you sleepy when you drink can protect against alcohol dependence.

The benefits of marijuana: Things are far from all bad for weed

Marijuana can certainly be beneficial.

It’s true that essentially every drug has some abuse liability. However, somewhere in the vicinity of 85% of those who try any given drug will never develop abuse or addiction problems (yes there are probably variations based on specific drugs, but that’s a good estimate).  As we all know, marijuana is a drug that receives a lot of attention and drives intense debate when it comes to its benefits and harms.  While most of the posts on my site focus on the other 15%, there is, and continues to be, evidence for the benefits of marijuana and other drugs that directly activate cannabinoid receptors.

Some of the shown benefits of marijuana

THC, the active ingredient in cannabis, is known to cause sedation, euphoria, decrease in pain sensitivity, as well as memory and attention impairments.  But there are some aspects of the cannabinoid receptors that have been shown to be effective in AIDS, glaucoma and cancer treatments.

Stimulation of cannabinoid receptors causes an increase in appetite and therefore helps with the wasting syndrome often seen as a side effect in AIDS treatments or those with eating disorders. Since THC activation decreases intra-ocular pressure, another area in which marijuana has been proven to be effective is in the treatment of glaucoma.  THC’s anti-emetic (or anti-vomiting) properties also make it a very useful tool for combating the side effects of cancer treatments.

Still, the activation of cannabinoid receptors is not synonymous with smoking weed. In fact, there are a number of other possible ways to consume THC and other cannabinoid-receptor activators. Also, THC is a potent immune suppressing agent, so in someone who already has a compromised immune system, such as AIDS patients, marijuana and other THC compounds could increase the risk of infection.

Future promise for the use of THC in medicine

There is some evidence that of the 2 major THC receptors (CB1 and CB2), one is associated with the immuno-suppression that occurs after chronic usage and the other is associated with the the more beneficial aspects we’d discussed. In the future, we may be able to produce a compound that activate only the behavioral effects and could therefore be used more safely for AIDS patients. Marijuana lovers will say that we should leave things as they are, but I’m all for less immuno-suppression with my cancer therapy.

Again, just because activation of THC receptors can provide the above benefits does not necessarily mean one should smoke marijuana. As usual, the benefits and risks have to be considered and one has to reach an educated, informed, conclusion. Still, there’s little doubt that in some situations, the use of marijuana, or other THC activators is not only prudent, but indeed recommended.

Co-authored by: Jamie Felzer

Kids perceive regular marijuana use less risky – Some tips.

The pendulum swings again. After years of decreases in use and in perceptions about use, a recent report indicates that high-school kids are once again beginning to use , and consider less risky the use of, marijuana.

The movement is no doubt part of a semi-regular cycle. After lack of awareness about prescription drugs and a significant increase in their abuse among children, this most recent trend shouldn’t be so surprising as the focus on marijuana has waned.

I think we need quite a bit of research to see if such increases do correlate with significant increases in individuals seeking help for marijuana-use-related problems. Yes marijuana advocates, those people exist whether you like it or not. For some proof, check out this link for a site put together by a recovering marijuana addict.

My quick, short, tips:

  1. If you use weed, use a vaporizer to avoid the toxic fumes that can cause cancer in much the same way cigarette smoke does.
  2. If your use becomes regular, whether daily or multiple times a week, consider talking to someone to help you figure out if you might be developing a problem use pattern. Those are much easier to stop early in their development.
  3. Pay close attention to the interference between your marijuana use and other life-commitments. This is a tale-tale sign of problems.