The term opioid is often synonymous with heroin: a highly addictive substance that can quickly lead to addiction.
However, opioids are synthetic drugs that encompass a wide range of different substances – from fentanyl to prescription painkillers, such as codeine.
In small and managed doses, opioids can be useful for managing pain. It is not uncommon for post-surgery patients to be given morphine – a strong opioid pain killer.
Whether consumed in small doses or used recreationally, opioids can have a wide-ranging impact on the body.
This article will discuss the effects of opioids on the body.
One of the most significant impacts of opioid consumption is how it affects the brain.
When an opioid is consumed, it goes straight to the brain and affixes to receptors, which then trigger neurons; this can lead to the release of neurotransmitters such as dopamine.
Dopamine affects many aspects of behaviour and psychical functions, such as feelings of pleasure, motivation, and general mood.
It is dopamine that initially causes a drug high but is also responsible for the desire to take more.
However, like many substances, people will gradually build a tolerance. The more someone takes, the more they will need to achieve the desired effect.
Prolonged consumption will lead to psychological and physiological dependency.
In addition, repeated use of opioids will gradually lead to more neuron activation in the prefrontal cortex – the area of the brain responsible for making decisions.
Studies have shown that continuous opioid use can lead to poor decision-making, a lack of inhibitions, and an inability to control behaviour.
Another outcome of this is the impact it has on performance – performance, in this sense, refers to motor functions and bodily and physiological tasks.
For example, studies have found that opioid consumption can negatively impact complex and divided attention tasks: driving, cooking, or typing, for example.
However, such negative effects are more common in people that lower tolerance level: people that have no, or minimal, history of using opioids.
Conversely, long-term opioid users who have built a tolerance can often perform tasks uninhibited.
Studies have also shown that opioids can lead to a loss of brain cells. As a result, this can damage areas of the brain associated with how a person thinks and feels.
Loss of brain cells can also lead to permanent cognitive impairment. (1)
One of the main purposes of opioids is pain relief. It achieves this, in part, by interacting with the central nervous system (CNS).
The CNS, essentially, is an individual’s spinal cord and brain. It is a communicative system that is responsible for the majority of bodily functions – this includes motor functions, sensory experiences, and even how an individual thinks and feels.
Opioids primarily affect the nervous system in three ways.
The first effect is that it lowers consciousness, potentially leading to sedation and drowsiness.
Secondly, it affects the CNS by inhibiting both psychomotor and cognitive skills.
Finally, it binds to neurons leading to potentially toxic effects and can lead to hyperalgesia – a heightened sense of pain – and involuntary shakes and spasms. (2)
Recent studies have found that opioids can affect the body’s immune system in various negative ways.
Primarily, evidence suggests that opioids suppress the immune system, increasing the risk of infection – particularly for those who regularly consume opioids.
The immune system is made of two essential components: innate and adaptive immune systems.
The innate system is the first line of defence against microorganisms – whether infection or disease. The adaptive immune system develops by building resistance over a period – this can range from days to weeks.
Opioids negatively impact these systems. Morphine, for example, has been found to impair macrophage function – these are special cells that help combat infection and disease.
It should be noted, however, that the data for the effects of opioids on the immune system is still under empirical investigation; the data, therefore, is complex and incomplete. (3)
Opioids can also have an adverse effect on the digestive system.
Studies have shown that opioid use can negatively impact the gastrointestinal tract.
The gastrointestinal tract starts at the mouth, then goes through to the esophagus, then to the stomach, and finally the small and large intestines.
Opioids affect the gastrointestinal tract by affecting the muscles and cells that help coordinate and break down food.
This can lead to several problems, such as the inability to digest food, constipation and nausea, or more serious issues such as abdominal inflammation. (4)
One of the most documented effects of opioids is the impact it has on a person’s respiratory system.
The respiratory system is made up of organs and other bodily components that are responsible for breathing – such as the lungs, the trachea, the heart, and the diaphragm.
Opioids affect the respiratory system by suppressing respiration.
The reason that this occurs is that when a person consumes opioids it slows down the central nervous system which, in turn, makes breathing more difficult – this is referred to as respiratory depression.
Respiratory depression is one of the most serious consequences of continuous opioid consumption and is one of the most common causes of opioid fatalities.
Respiratory depression can lead to respiratory failure: when a person begins to lose consciousness and potentially stops breathing.
Because the person is under the influence of opioids, the brain’s function is reduced and often unable to wake the person up.
Reduced breathing is one of the first signs of an opioid overdose.
Further effects of opioids on the respiratory system include bronchospasm – the tightening of the airway muscles – and the constriction of blood vessels which can lead to increased blood pressure. (5)
Perhaps the most significant effect that opioids can have on the body is that it leads to dependency and then when without it, withdrawal.
Opioids are highly addictive and prolonged use will often lead to addiction – both psychologically and physiologically.
The former can occur due to the dependency upon the opioid to achieve a certain mental state, such as increased motivation or a positive mood. As the tolerance builds more opioids are required to achieve the same desired mental state.
Prolonged use will also increase the chance of a person needing the substance to function physiologically.
As the body becomes accustomed to the drug, the brain’s reward system becomes dependent upon it. To function properly and feel normal will require further consumption of the opioid.
Those with an opioid dependency are likely to experience withdrawal symptoms when they cease to take the substance regularly – this usually occurs between 6-12 hours after the final ingestion.
Withdrawal symptoms include nausea, depression, vomiting, and insomnia. More serious withdrawals symptoms include dehydration and respiratory issues.
Symptoms can last up to several weeks but usually subside within several days. (6)
(1) Ballantyne, Jane C. “The brain on opioids.” Pain 159 (2018): S24-S30; and, Jensen, T. S. “Opioids in the brain: supraspinal mechanisms in pain control.” Acta anaesthesiologica scandinavica 41, no. 1 (1997): 123-132.
(2) https://pubmed.ncbi.nlm.nih.gov/17430825/; and, Holzer, Peter. “Opioids and opioid receptors in the enteric nervous system: from a problem in opioid analgesia to a possible new prokinetic therapy in humans.” Neuroscience letters 361, no. 1-3 (2004): 192-195.
(3) https://pubmed.ncbi.nlm.nih.gov/8947928/; and, Sacerdote, Paola. “Opioids and the immune system.” Palliative medicine 20, no. 8_suppl (2006): 9-15.
(4) https://pubmed.ncbi.nlm.nih.gov/2838107/
(6) Redmond Jr, D. E., and J. H. Krystal. “Multiple mechanisms of withdrawal from opioid drugs.” Annual review of neuroscience 7, no. 1 (1984): 443-478; and, Shah, Mansi, and Martin R. Huecker. “Opioid withdrawal.” (2018).
Boris is our editor-in-chief at Rehab 4 Addiction. Boris is an addiction expert with more than 20 years in the field. His expertise covers a broad of topics relating to addiction, rehab and recovery. Boris is an addiction therapist and assists in the alcohol detox and rehab process. Boris has been featured on a variety of websites, including the BBC, Verywell Mind and Healthline. You can connect with Boris online at LinkedIn or X.com.
