Opium and marijuana are two very different substances. Opium is derived from the opium poppy plant and has been cultivated and in use, since around 3,400 B.C.

Marijuana, or weed, comes from the Cannabis sativa plant and has been around for over 12,000 years. Opium and weed differ in their mechanisms of action, their effects on the human body, their level of clinical usefulness, and their relative risk for addiction.

These substances are very different, but still the question remains – what’s the difference between opium vs weed?

The Mechanism of Action: Opium vs. Weed

Mechanism of action refers to the way in which a drug exerts its effects on the human body. Opium and weed each have a distinct mechanism of action.

Once opium enters the body, it binds to opioid receptors. There are four main types of opioid receptors; the one that is bound by most “abused opioids” like opium is the mu-opioid receptor.

The majority of mu-opioid receptors are found in an area of the brain known as the limbic system. The limbic system is involved in memory formation, motivation, and emotional responses.

Once bound, opium exerts its effects on the body, which are discussed in more detail below.

When weed is ingested, its active ingredient–delta-9-tetrahydrocannabinol (i.e. THC)–binds to cannabinoid receptors in the body. There are two main types of cannabinoid receptors; the one that THC binds to mainly is the CB1 receptor.

The majority of CB1 receptors are found in areas of the brain including the frontal cortex, the cerebellum, and the basal ganglia. These areas of the brain are involved in cognition and movement.

Once bound, weed exerts its effects on the body, which is discussed in more detail below.

Though opium and weed have very different mechanisms of action, they have similar effects on the brain by virtue of the fact that they are both addictive substances. All addictive substances lead to a rapid and intense release of the neurotransmitter dopamine into the brain.

The intense feeling of pleasure that this dopamine release induces each time a substance is used is what contributes to the development of substance use disorder disorder/addiction.

How Do Weed and Opium Affect the Body?

Most people know that when an opiate like opium is ingested, an individual may experience pain relief, feelings of euphoria, and a sense of calm. But opium has even more effects on the human body.

When opium binds to mu-opioid receptors, it can impact the brain, the digestive system, and the immune system. Mu-opioid receptors in the brainstem have an inhibitory effect on the respiratory centers in the brain.

If an individual uses too much of an opiate, his or her respiratory center may become so profoundly inhibited that he or she stops breathing and dies. Mu-opioid receptors in the digestive system have an inhibitory effect as well.

Use of opiates in the short and long-term can lead to constipation. In addition, mu-opioid receptors have a suppressive effect on the immune system. Those who use or abuse opiates are at high risk for infections.

Like opium, weed can provide pain relief once its active ingredient binds to CB1 receptors. Weed can also stimulate appetite. Also like opium, weed can have negative effects on the body and lead to constipation.

More serious, negative side effects associated with weed involve the areas of the brain where most CB1 receptors are found and include “impaired motor coordination,” “impaired judgment,” and memory loss.

Clinical Usefulness: Opium vs. Weed

Some substances classified as opioids are clinically useful. For example, medications such as Vicodin and Oxycontin are opioids that are indicated in the treatment of severe pain that is associated with traumatic injury, major surgery, and cancer.

When opioids are used appropriately by healthcare providers and their patients, opioids can offer very needed pain relief. When opioids are misused, however, individuals have a higher likelihood of becoming addicted, overdosing, and dying.

When it comes to illicit opioids like heroin and opium, these drugs have absolutely no utility in the clinical setting. Heroin and opium are highly addictive substances that can easily lead to overdose and death.

Similarly, weed, or its active component THC, can be clinically useful. THC–in the form of the medications Marinol or Cesamet–is often used as an appetite stimulant in patients battling cancer or AIDS.

With the help of these medications, patients may regain their desire to eat, gain weight, and avoid wasting. Current research is also investigating how weed can be used to treat disorders as diverse as chronic pain and epilepsy.

At the same time, misuse or abuse of weed can lead to very negative side effects. Long-term use of weed can lead to structural brain changes associated with memory loss and a loss of cognitive abilities.

While the risk of addiction is quite low, there have been reports of individuals who identified themselves as being addicted to marijuana.

Opium vs. Weed – Which is More Addictive?

Opium and weed differ greatly in their relative risk for addiction. In Basic & Clinical Pharmacology, Dr. Christian Luscher–an expert on drugs of abuse–introduces a relative risk of addiction scale.

A drug with a rating of 1 has the lowest risk for addiction, whereas a drug with a rating of 5 has the highest risk for addiction.

Opium has a relative risk of 4. Weed, on the other hand, has a relative risk of 2. Clearly, the risk for addiction is much higher with opium vs. weed.

Opium and weed are two distinct drugs with addictive potential. If you or someone you know is battling an addiction with either of these drugs, help is available. You don’t have to fight alone.