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Addiction is a chronic, relapsing disorder involving changes in brain reward, motivation, learning, stress and executive control systems. While different substances (and behaviours) act through distinct primary mechanisms, they converge on common neurobiological pathways — particularly the mesocorticolimbic dopamine system.

Below is an overview in Australian English of the core mechanisms and then substance-specific and behavioural addiction processes.

Core Neurobiological Pathways in Addiction

1. The Mesocorticolimbic Dopamine System

The central pathway implicated in addiction is the mesocorticolimbic circuit, involving:

• Ventral tegmental area (VTA)
• Nucleus accumbens (NAc)
• Prefrontal cortex (PFC)
• Amygdala
• Hippocampus

All addictive drugs increase dopamine transmission in the nucleus accumbens, either directly or indirectly. Dopamine does not simply produce pleasure — it encodes reward prediction, salience and learning. With repeated exposure:

• Drug-related cues gain exaggerated salience
• Natural rewards become less reinforcing
• Behaviour becomes increasingly habitual and compulsive

2. Neuroadaptation and Allostasis

Repeated substance exposure produces:

Tolerance — Reduced response due to receptor downregulation or neurotransmitter depletion.

Dependence — Neuroadaptations that produce withdrawal when the substance is removed.

Allostatic shift — The brain’s reward set point shifts downward, mediated by stress systems (e.g. corticotropin-releasing factor), resulting in dysphoria during abstinence.

3. Habit Formation and Loss of Control

With repeated use:

• Control shifts from ventral striatum (goal-directed) to dorsal striatum (habit-based)
• Prefrontal cortex regulation weakens
• Impulsivity and compulsivity increase

Substance-Specific Mechanisms

Alcohol

Alcohol acts on multiple neurotransmitter systems:

• Enhances GABA-A receptor function (inhibitory)
• Inhibits NMDA glutamate receptors (excitatory)
• Increases dopamine release in nucleus accumbens
• Affects endogenous opioid systems

Chronic exposure leads to:

• GABA downregulation
• NMDA upregulation
• Hyperexcitable state during withdrawal (risk of seizures, delirium tremens)

Alcohol dependence also involves stress system activation and impaired frontal cortical control.

Methamphetamine

Methamphetamine is a potent psychostimulant that:

• Enters presynaptic terminals
• Reverses the dopamine transporter (DAT), causing carrier-mediated dopamine efflux
• Inhibits vesicular monoamine transporter 2 (VMAT2), releasing dopamine from synaptic vesicles into the cytoplasm
• Causes massive dopamine release into the synapse

It also increases noradrenaline and serotonin.

Chronic use causes:

• Dopamine neurotoxicity (particularly to dopaminergic terminals)
• Reduced dopamine transporter availability
• Structural changes in striatum and PFC
• Persistent cognitive deficits

Methamphetamine produces particularly strong sensitisation of cue-driven craving.

Cocaine

Cocaine:

• Blocks the dopamine transporter (DAT), preventing reuptake
• Increases synaptic dopamine concentration

Unlike methamphetamine, cocaine acts by blocking DAT rather than reversing it, and does not cause large presynaptic vesicular release — the elevation in synaptic dopamine arises from impaired clearance.

Repeated use leads to:

• Dopamine receptor downregulation
• Enhanced cue reactivity
• Rapid cycling between intoxication and crash
• Strong psychological dependence

Opioids (e.g. heroin, morphine, oxycodone)

Opioids act primarily at mu-opioid receptors (MORs), which are expressed throughout the brain, including in the VTA. Their dopaminergic effects arise through multiple mechanisms:

• MORs on GABAergic interneurons in the VTA suppress inhibitory tone, thereby disinhibiting dopamine neurons (the classical disinhibition mechanism)
• MORs are also expressed on VTA dopamine neurons and projection targets directly, contributing additional excitatory drive beyond the disinhibition pathway

They also act in brainstem respiratory centres, which underlies the risk of respiratory depression in overdose.

Chronic use produces:

• Receptor desensitisation and internalisation
• Reduced endogenous opioid production
• Severe physical withdrawal mediated by noradrenergic rebound in the locus coeruleus
• Strong negative reinforcement (use to avoid withdrawal)

Cannabis

Δ9-tetrahydrocannabinol (THC):

• Activates CB1 receptors (the primary psychoactive cannabinoid receptor)
• Modulates GABA and glutamate release at presynaptic terminals
• Indirectly increases dopamine in NAc via disinhibitory mechanisms

Cannabis produces:

• Altered endocannabinoid system function
• CB1 receptor downregulation with chronic use
• A mild to moderate withdrawal syndrome (irritability, sleep disturbance, appetite changes)
• Effects on hippocampal memory circuits

While addiction risk is generally considered lower than for opioids or stimulants, it remains clinically significant and may be underestimated, particularly given the widespread availability of high-potency THC products (e.g. concentrates and high-THC flower), which are associated with greater dependence risk and more severe withdrawal.

MDMA (Ecstasy)

MDMA:

• Reverses the serotonin transporter (SERT), causing massive serotonin efflux — this is its primary mechanism
• Also increases dopamine and noradrenaline

Neurobiological consequences include:

• Acute empathogenic and entactogenic effects driven by serotonin release
• Post-use serotonin depletion, which may contribute to dysphoria in the days following use
• Potential serotonergic neurotoxicity, though this evidence comes largely from high-dose or repeated animal studies; the clinical significance in typical human recreational use remains under debate and is not definitively established
• Moderate addictive potential relative to psychostimulants, partly because dopaminergic effects are less prominent than with cocaine or methamphetamine

Prescription Psychoactive Medications

Certain prescribed medications also have addictive potential:

Benzodiazepines — Enhance GABA-A receptor activity. Cause tolerance via receptor downregulation. Dependence is primarily a GABAergic adaptation. Withdrawal can be protracted and, in cases of high-dose or long-term use, may produce seizures.

Prescription stimulants — Act via similar mechanisms to amphetamine, increasing dopamine and noradrenaline. Risk of misuse exists in susceptible individuals, though therapeutic doses in appropriately diagnosed patients are associated with substantially lower addiction risk than recreational use.

Behavioural (Process) Addictions

Gambling Disorder

Gambling disorder is recognised in DSM-5-TR as a non-substance-related addictive disorder. Although no substance is ingested, similar neurobiological mechanisms are involved.

Dopamine and reward prediction error — Near misses activate the nucleus accumbens similarly to wins. Variable ratio reinforcement schedules (as in poker machines) generate strong, unpredictable dopamine prediction error signalling that powerfully drives continued behaviour.

Cue reactivity — Gambling-related cues activate the same mesocorticolimbic circuitry as drug cues, with increased striatal activation and reduced prefrontal inhibitory control.

Habit circuitry — A shift from ventral to dorsal striatal control contributes to compulsive betting despite continued losses.

Other Emerging Behavioural Addictions

Conditions such as internet gaming disorder, compulsive sexual behaviour disorder, and problematic social media use share overlapping neurobiological features including:

• Dopamine dysregulation and sensitisation to cue salience
• Reduced executive control
• Stress system activation

However, the evidence base for most of these conditions is still developing, and their classification as formal addictive disorders remains an area of active research and debate. Internet gaming disorder is currently listed in DSM-5-TR as a condition for further study.

Shared Neurobiological Themes Across Addictions

Across substances and behaviours, addiction involves:

• Dopamine sensitisation to cues
• Reduced sensitivity to natural rewards
• Impaired prefrontal inhibitory control
• Stress system overactivation (particularly corticotropin-releasing factor)
• Habit circuitry dominance (dorsal striatum)
• Neuroplastic changes in glutamatergic signalling

Why Some Substances Are More Addictive

Addictive potential is influenced by multiple interacting factors. The speed of dopamine rise is one of the most studied — faster onset of dopamine elevation (e.g. via smoking or intravenous administration) is associated with stronger reinforcement. This framework, developed largely through the work of Volkow and colleagues, has strong empirical support, though it represents a mechanistic model rather than an established universal law. Other important factors include:

• Intensity of dopamine release
• Pharmacokinetics (e.g. route of administration)
• Withdrawal severity (which drives negative reinforcement)
• Social and environmental context
• Genetic vulnerability (heritability of addiction is estimated at 40–60% across substances)

Conclusion

Addiction is not simply about pleasure seeking. It reflects maladaptive neuroplasticity in reward, stress, learning and executive control circuits. While alcohol, methamphetamine, cannabis, opioids, cocaine and MDMA each act through different primary molecular mechanisms, they converge on common neural pathways that drive craving, tolerance, withdrawal and compulsive use. Behavioural addictions such as gambling engage these same circuits despite the absence of an ingested substance.

The neurobiological understanding of addiction continues to evolve, and where evidence is still emerging — particularly regarding emerging behavioural addictions and the long-term neurotoxic effects of substances like MDMA — clinical interpretation should be appropriately cautious.

As I always like to say, there are as many reasons why people self-sabotage as there are people. A common theme is to protect the self from failure, feeling things we don’t want to feel, and to control our experiences.

One of the hidden culprits behind self-sabotage is the need for perfection and control. Self-sabotage has a strange way of helping us maintain the illusion that if only we had put in more effort or had better circumstances, everything would have worked out as it should. Social psychologists call this counter-intuitive strategy of regulating self-esteem ‘self-handicapping.’ It’s very seductive to engage in self-sabotage because the hidden payoff is high. It’s often easier to be a perfect whole rather than a real part. It’s a short-term solution that sidesteps the more arduous but ultimately more fulfilling work of individuation and self-realization. It takes risk, patience, suffering, and ultimately wisdom to come to the place where you can let go of self-sabotage and learn how to be real.

Behaviour is said to be self-sabotaging when it creates problems in daily life and interferes with long-standing goals. The most common self-sabotaging behaviors include procrastination, self-medication with alcohol and other drugs, comfort eating, and forms of self-injury such as cutting.

Self-sabotage originates in the internal critic we all have, the side that has been internalized by the undermining and negative voices we’ve encountered in our lives. This critic and ‘internal sabotuer,’ functions to keep the person from risking being hurt, shamed, or traumatized in the ways they had been in the past. While it keeps the individual safe, it does so at a very high cost, foreclosing the possibility of new, creative, and three-dimensional experiences. Like an addiction, self-sabotage insidiously lulls and deludes us into thinking that it has the answer. In fact, it is the problem masquerading as the solution. Nothing stops self-sabotage faster in its tracks than shining this particular light on it. Consciousness is true power. We need to let go of our illusions of omnipotence and perfection and see that it is only when we are real and imperfect that we can create a true work of art. Then and only then we can enjoy the gifts of being Real.

– Michael Alcée, Ph.D., Relational therapist/ Clinical psychologistArt: Bawa Manjit, Acrobat

– Self-Sabotage | Psychology Today Australia

Adapted from Australian Institute of Professional Counsellors, Institute Inbrief, Edition 359.

Good day readers! How are you? … Shit? Depressed? Anxious? Angry? First of all, if you’re someone who says “I feel shit”, I would encourage you to use a more accurate descriptor instead of shit. Tell your brain what emotion or feeling you are experiencing. Shit can mean a lot of things. When we’re able to identify an emotion, it’s more likely we’ll be able to regulate or manage it. When I was learning Dialectical Behavioural Therapy, they had a saying: Name it to claim it to tame it. They also encouraged us to distance our identity from our feelings e.g., “I’m having the feeling that I’m angry” rather than “I’m angry”. I know it sounds like simple fluff but there is a profound difference between observing the experience of anger, loneliness, fear, guilt etc. and believing we (the self) are the embodiment or a manifestation of an emotion.

Alright, moving along to the subject of the article. The Australian Institute of Professional Counsellors sent me their monthly (I think it’s monthly) Institute Inbrief. If you’re someone who has lived with a mental health disorder or emotional difficulties for a long time, being in nature is not really a new antidote from the field. And it’s not always as simple as just going out into nature. When I was deep in the abyss of my own depression, there wasn’t a lot that would change my mood or perception of life. But, we do these practices anyway – and that’s kind of the point. It’s a practice. It may have to be initiated using a bit of self-force. Oftentimes, motivation comes after we begin the motion.

So, here are some examples from the article that support ‘nature has a therapeutic effect for the mind and body’:

• One study found that women who looked at pictures of nature for two minutes had lower levels of the stress hormone cortisol (Gillespie, et al., 2019).
• Another study showed that people who walked in a forest preserve showed lower levels of hostility, aggression and anxiety than they did before the walk.
• Gregory Bratman, PhD, an assistant professor at the University of Washington, and colleagues shared evidence that contact with nature is associated with increases in happiness, subjective well-being, positive affect, positive social interactions and a sense of meaning and purpose in life, as well as decreases in mental distress (Science Advances, Vol. 5, No. 7, 2019).

How can we most effectively reap the mental health benefits that nature offers?

Why nature?

I’m aware we’re in Covid-19 lockdown and restrictions at the moment (27/09/2021) so you will need to determine for yourself if what proceeds to be written is practical and realistic for you right now.

We need to understand that the psyche of the human-being is linked to the natural world in many important ways. The human brain constantly processes and assimilates incoming information, and it relies on external stimuli for guidance regarding how to think and behave. Not only does incorporating nature into our daily lives help us understand the world better, but it can also contextualise ourselves in accordance with this understanding; humans – as an animal – have evolved in tandem with the natural world, and thus it is able to promote the development of beneficial skills including improved visual–spatial acuity, attentional abilities, and memory (Oddie, 2019). Our world is full of beautiful and intricate natural structures, and even just a simple walk through a park can provide us with moments of joy, awe, and wonder (Fiebert et al., 1980; Lefebvre & Brucker, 2018).

Additionally, the seemingly chaotic stimulus that nature provides us with promotes creativity and abstract thought (Berman, et al., 2012); these qualities have been the cornerstone of our species’ evolutionary development over the past few thousand years, thus illustrating the primacy of our relationship with nature.

Our neurobiology is extremely complex, and as such cannot be reduced to simple terms. However, we can say with some certainty that our brains’ sophisticated processing systems are enhanced by our interactions with nature. Our brain naturally integrates external stimuli into existing mental frameworks—this is referred to as “cognitive recursion” (Oddie, 2019). This means that if we spend our time in environments that were designed and created by the human mind, then we are putting ourselves in an echo chamber of stimulus and will not receive new information to broaden our mental capabilities. If we spend time in nature surrounded by structures and patterns that are born of unfathomably complex and foreign processes, then our minds can assimilate this new content into its existing understanding of reality.

Basically, if you spend your days in a white cube (i.e. a house) then your mental framework will be limited to the creative potential that a white cube suggests. If, however, you spend your days in an ever-changing fractal world of colours and shapes (i.e. natural environments) then your mind will reflect this, and adopt an expanded creative potential in order to perceive and understand its surroundings. This is a powerful reality; understanding how our connection with nature nourishes our minds is where spirituality meets both science and intuition.

What benefits does nature offer?

Perhaps the most important and relevant aspect of an active lifestyle in nature is its ability to reduce stress. Studies have shown that taking a walk in a park could decrease stressful thoughts, and even reduce blood pressure (Bush, et al., 2016; Robins, 2020). This finding demonstrates that simply being exposed to nature can decrease stress levels, and implies that returning to nature may be an effective way of keeping our mental health at its best. And here’s the kicker: any amount of time spent in nature is net-gain for your mental wellbeing (Robins, 2020). There is no threshold or minimum a dosage of nature that will have an effect on you – even just spending a short time sitting in your backyard enjoying nature will likely have a positive impact on your mental health.

Other studies have also shown that exposure to nature has an effect on our emotional outlook; particularly in regards to relieving us from pessimistic and fearful thinking (Lefebvre & Brucker, 2018). Life in the modern world is full of consequential decisions and options, the outcomes of which can dictate the quality of your entire life. Decision making is one of the more neurologically complex and taxing processes that our brains undertake, and research has shown that we make 35,000 choices per day (Huston, 2018).

This process involves assessing each option for its individual merit, sorting each option into a hierarchy in relation to every other option, making predictions about every possible positive and negative outcome of each option, and then weighing each outcome against that of every other option; golly, how exhausting! The fear and pessimism arises because each option invariably comes with the potential for myriad negative outcomes, and we are constantly coerced into assessing these. Thankfully, nature offers respite from all this noise. Spending time in nature relieves us from overthinking by presenting us with very few options, each with relatively inconsequential outcomes; ‘where will I sit while I drink from my water bottle?’ or ‘should I take the path leading towards the lookout, or the waterfall?’ are not taxing decisions to make, and will not prompt fearful or pessimistic thought patterns. There is an easiness to natural environments in which things seem to flow along their own course, and we are able to simply jump into the stream and flow along with it.

Aside from experiential benefits, time in nature can help us orient ourselves in the world in more grounded and productive ways. In today’s society, our attentional abilities are sapped by large corporations who profit from our distractibility, and it seems as though a way to remedy this mental breach is routine contact with nature. Attentional abilities are bolstered by spending time in nature (Ebata & Izenstark, 2017), making you less susceptible to the temptations of modernity (i.e. problematic social media scrolling, binging streaming services, etc).

Thus, making time in nature a priority in our lives – especially when we do not even feel stressed or anxious – can help us orient ourselves to the world around us and find a sense of personal empowerment. Taking time to be immersed in nature can help us regain confidence, ground us in a personal sense of meaning, and re-establish our wellbeing. Being in nature is correlated with increased positive emotions and feelings of control over one’s life (Chowdhurry, 2021), so even if we do not believe we need some sort of mental intervention, the benefits are there for everybody to experience.

How can I fit more nature-time into my life?

For the most part, we only need to reflect on our daily behaviours to see how we can incorporate time in nature into our lives. James Clear, in his wildly popular book Atomic Habits (2018), suggests incorporating a “budding habit” into an existing habit.

So for instance, if you have a lunch break during the work day, you could spend it outside on a park bench instead of in the staff room. If you come home at the end of the day and like to sit on the couch with a book, go outside and sit on the grass instead. These are simply ways to adopt more nature-time into your life, without having to add another separate activity to your schedule. In a 2017 study (Austin, et al., 2017), some participants were asked to take a brief walk in nature once per day, and other participants weren’t. The results showed that those who walked daily had higher levels of positive emotions and well-being than those who walked less. It doesn’t take a lot of time to nourish our minds in the deep ways that only nature offers us, and it seems to be a worthwhile habit to form.

Making the time to experience nature is easy to ignore in lieu of more ‘important’ tasks. That walk in the park you planned on taking this afternoon suddenly seems overshadowed by a looming deadline or a sink full of dirty dishes. For this reason, it can be beneficial to keep yourself accountable by planning nature-time with other people. Planning to go for a walk with friends means there is a lower likelihood of cancelling. Better yet, if you can join a weekly community group or class of some sort then you won’t even have to continually plan your time in nature.

There are volunteer groups who aid revegetation in nature reserves, there are community gardens who need people to tend to plants and crops, and there are clean up groups who dispose of discarded rubbish in bush-lands. If volunteering isn’t appealing to you, then you could change your routine by canceling your gym membership in lieu of outdoor exercise classes or yoga, or even new activities like cycling or rowing. Making scheduled appointments to spend time in nature can assist those who have trouble achieving this with sheer willpower, and your mental health will thank you for it.

Our acknowledgment of the value of time spent in nature is growing each day, which is why more urban living environments are incorporating ‘green spaces’ into their design. Using the latest neuroscience research, we are able to determine which types of natural environments compliments our mental states the most effectively. For example, it has been found that areas with high levels of biodiversity can alleviate symptoms of anxiety and depressions more-so than those with low levels of biodiversity (Wyles, et al., 2019). Similarly, people who watched videos featuring a diverse array of flora and fauna reported lower anxiety and higher vitality than those who watched videos of less biodiverse landscapes (Wolf, et al., 2017).

Findings like these offer valuable insight into how we can engineer our surroundings to best facilitate the highest levels of wellbeing possible. It is clear that spending time in nature is invaluable for our mental health, but a half-hour lunch break doesn’t give us time to go hiking through a biodiverse mountain landscape; what we can do, however, is have access to green spaces which replicate the stimulus that we would receive if we were in nature. This has proven to be an eloquent solution to the pressing issue of depression rates in urban CBD areas (Ebata & Izenstark, 2017).

Summary

In conclusion, the role of nature in our lives is of paramount importance to our health and should be a priority for us all. Although it may feel like adding a daily walk outside to our schedules would be in futility, the positive mental health benefits outweigh the costs significantly. Making time in nature a priority, no matter how little, can greatly increase our overall sense of wellbeing, and remind us that we are interconnected to the living world around us.

There is no minimum threshold required to reap the benefits of nature, so we can all find a way to capitalise on just a little bit of time in natural environments. As a species, it is our natural disposition to enjoy the outdoors, and the benefits are more abundant than you might expect. So pop on a pair of joggers, Google search ‘hikes near me’, phone a friend, and get out there amongst the fresh air; you can thank us later!

References:

1. Berman, M. G., Kross, E., Krpan, K. M., Askren, M. K., Burson, A., Deldin, P. J., . . . Jonides, J. (2012, November). Interacting with nature improves cognition and affect for individuals with depression. Retrieved from: Website.
2. Bush, R., Dean, J., Lin, B., & Fuller, R. (2016). Health Benefits from Nature Experiences Depend on Dose. Scientific Reports.
3. Chowdhury, M. (2021, February 19). The Positive Effects Of Nature On Your Mental Well-Being. Retrieved from: Website.
4. Clear, J. (2018). Atomic habits: An easy and proven way to build good habits and break bad ones. London: RH Business Books.
5. Hunter, M. R., Gillespie, B. W., & Chen, S. Y. (2019, March 15). Urban Nature Experiences Reduce Stress in the Context of Daily Life Based on Salivary Biomarkers. Retrieved from: Website.
6. Huston, M. (2018). How Many Decisions Do We Make Each Day? Retrieved from: Website.
7. Izenstark, D., & Ebata, A. (2017). The Effects of the Natural Environment on Attention and Family Cohesion: An Experimental Study. Children, Youth, and Environments.
8. Wyles, K. J., White, M. P., Hattam, C., Pahl, S., King, H., & Austen, M. (2017). Are Some Natural Environments More Psychologically Beneficial Than Others? The Importance of Type and Quality on Connectedness to Nature and Psychological Restoration. Environment and Behavior, 51(2), 111-143. doi:10.1177/0013916517738312