Archive for June, 2012

Ceci n’est pas la marijuana…

“You have been assigned to the condition to smoke an active marijuana cigarette that contains THC. THC is the primary psychoactive cannabinoid that gets people high.”

Does the fact that you are told you are taking a drug effect your reaction to that drug… or the drug’s effect itself? This was the simple question posed by a group of researchers publishing in Psychopharmacology. The effect of taking a drug is one thing. The effect you expect it to have is something altogether different.

“…users believing they are smoking marijuana may compensate for expected intoxication effects when engaged in deliberate decision-making by making less impulsive and risky decisions.”

34 subjects at a time were given the task to smoke a cigarette that contained marijuana or a cigarette that contained a placebo. Participants were selected based on an interesting set of criteria; native English speakers, 18 to 30 years of age, frequent marijuana use over the past month (at least once a week and at least ten times in the past 6 months), and self-reported ability to abstain from marijuana for 24 h without withdrawal.

This was a balanced placebo design experiment, examining the relative effects of expecting to receive active marijuana. These regular marijuana smokers, randomly assigned into one of four groups:

  • Told they were getting THC but got a placebo

  • Told they were getting THC and got THC

  • Told they were getting a placebo but got THC

  • Told they were getting a placebo and got a placebo

All rather deceitful and standard practice for a placebo trial.

What came next was probably the most regimented smoking session the participants had ever undertaken. Smoking sessions occurred in a 75-square-feet ventilated smoking room, with standard-issue humidified cigarettes that are rolled at both ends. And smoked according to the “standardized paced puffing procedure” — until the ash reached a mark 10 mm from the end.

Subjects and participants were then evaluated for subjective intoxication, behavioral impulsivity, and decision-making related to risky behaviours.

The laboratory test known as the Stop Signal Task is one commonly employed as a laboratory measure of inhibitory control. In essence, it uses an external stimulus to signal participants to interrupt or inhibit an already-initiated motor response. Simply put, subjects are asked to respond as fast as they can to symbols on a screen. Then an auditory tone tells the participant that they are to try and withhold their response to the current symbol on the screen. The tone occurs occasionally, in an unpredictable way, and at various latencies after the appearance of the letter on the screen. The stop signal reaction time, is an estimation of the time an individual needs to stop their usual behavior in response to the stop signal. Active THC, regardless of whether subjects were told or expected it, impaired inhibition on the Stop Signal Task.

Out of all the participants only a small proportion suspected that they were being deceived. Suspicions about the THC content were only reported by two participants (in the Told THC/Received Placebo condition) and by seven participants (in the Told Placebo/Received THC condition). In all cases, Both THC dose and marijuana expectancy independently increased subjective intoxication.

It is commonly known that real or perceived expectancies can play a part in influencing responses to other drugs, such as alcohol. Here, expectancy of smoking THC in combination with active THC increased perceptions of risk from risky alcohol use.

The effect of THC somewhat contributed to impaired inhibition — that is the pharmacological effect and not the perceived effect. Whereas expectancy of having smoked THC affected impulsive decision-making, with a compensatory direction of effect on some measures of risky decision-making. For example, independently from the THC administration, expectancy also increased perceived risk from coercive sex among women.

Researchers showed that THC can affect some mechanisms underlying impulsive behaviors while not affecting others. The study represents the first evaluation of independent and combined effects of smoking and expecting to smoke active marijuana on multiple measures of risk taking and impulsivity, using a balanced placebo design. It proved a way to independently tease out the expectancy that marijuana was smoked from the pharmacologic effect of delta-9-tetrahydrocannabinol (THC).

Originally appearing at All Results Journals

Image — source

ResearchBlogging.org

Metrik J, Kahler CW, Reynolds B, McGeary JE, Monti PM, Haney M, de Wit H, & Rohsenow DJ (2012). Balanced placebo design with marijuana: Pharmacological and expectancy effects on impulsivity and risk taking. Psychopharmacology PMID: 22588253

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Slippery when wet…

It’s a trap!

In the fields of Brunei Darussalam in North Borneo, once a crown colony of Great Britain, lies the pitcher plant. The pitcher plant is carnivorous, capturing and devouring insects that seek to harvest its nectar.

The pitcher plant is beguiling, attractive, and has evolved many ways to seduce its predator. Insect prey is captured within the wells of its pitcher-shaped leaves, when insects crawling along it slip on the wax crystals of the inner wall, and fall into the digestive fluid at the bottom. A dense layer of platelet-shaped wax crystals, orientated perpendicularly to the surface for a reason — to essentially make it difficult for insects to grip — especially when wet.

The wax crystal layer is a common feature to many species of the pitcher plant. One such species, Nepenthes gracilis, is unusual in the fact that the crystals are also present on the underside of the pitcher lid.

This was the observation that led to recently published research describing a new way the pitcher plant captures its prey.

The lead author of the paper, published today in PLoS ONE, Dr Ulrike Bauer from the University of Cambridge’s Department of Plant Sciences, said: “It all started with the observation of a beetle seeking shelter under a N. gracilis lid during a tropical rainstorm. Instead of finding a safe — and dry — place to rest, the beetle ended up in the pitcher fluid, captured by the plant. We had observed ants crawling under the lid without difficulty many times before, so we assumed that the rain played a role, maybe causing the lid to vibrate and ‘catapulting’ the beetle into the trap, similar to the springboard at a swimming pool.”

In effect, it’s a clever strategy on the part of the pitcher plant. At times, mostly when the weather is dry, insects have no problem gathering nectar from the plant. This allows “scout” insects and ants to report back and ultimately means a larger number of insects are on their way back to the plant.

The trap is set.

In that field in Borneo it was a Coccinellid beetle that fell for the trap, being flicked into the well of the pitcher by a raindrop that bounced off the lid of the plant. The beetle had sought shelter from the rain but had found its ultimate demise instead. Researchers posited that the wax crystal layer, while providing a secure foothold under normal conditions, causes insects to detach more easily under sudden impacts.

Researchers replicated and simulated rain in the lab and its effect on ant colonies trying to gather nectar. Comparing this to real in-the-field settings showed that the lid itself goes a long way to contributing to prey capture.

In the fields of northern Borneo the rains are brief, heavy and intermittent. And the pitcher plant — with its canopy-like lid — makes an attractive refuge from the deluge. But the most interesting part suggests that N. gracilis uses much more than its simple lid to capture insects — but has also re-upped its nectar secretion in a way that increases attraction of its prey to the lower lid surface.

Dr Bauer added: “Scientists have tried to unravel the mysteries of these plants since the days of Charles Darwin. The fact that we keep discovering new trapping mechanisms in the 21st century makes me curious what other surprises these amazing plants might still have in store!”

A version of this appears in Australian Science Mag

Photo credit: Ulrike Bauer

ResearchBlogging.org

Bauer, U., Di Giusto, B., Skepper, J., Grafe, T., & Federle, W. (2012). With a Flick of the Lid: A Novel Trapping Mechanism in Nepenthes gracilis Pitcher Plants PLoS ONE, 7 (6) DOI: 10.1371/journal.pone.0038951

Addicted to Love…

The ultimate reductio ad absurdum argument is that any behaviour can become potentially addictive.

Which leads to the next logical question: are there any good addictions? Researchers today talk of addiction as a disease. And in that trope, the “disease concept” of addiction is really just a metaphor. A metaphor with connotations.

Researchers posit that for a behaviour to become harmfully addictive, it would involve some type of “rush” effect, time-intensive repetition, intense behavioural or cognitive preoccupation, loss of control, and negative consequences.

At this point in time, we have a long list of things that can be counted as addictive, including prayer, meditation, and even religion. But for now we focus on perhaps the oldest of all behaviours — love.

The relationship between passionate love and addiction has been debated exhaustively amongst social science circles for many years. It began with Sigmund Freud, who had intimated the existence of a similarity between amorous passion and drug addiction. Currently this is ill-defined. That is to say, there are no recognized or standard definitions or diagnostic criteria for “love addiction”, “love passion”, or “sex addiction”.

Is there a difference between love and addiction? Is being addicted to love a disease? Is social attachment an addictive behaviour?

All loaded questions with no easy answers. Some sort of parlance on the subject comes from the world experts in all things pertaining to love and sex — the French. A group of French researchers, publishing in The American Journal of Drug and Alcohol Abuse, describe the clinical distinctions between “love passion,” “love addiction,” and “sex addiction”. Using advances in neurobiology to compare clinical, neuropsychological, neurobiological, and neuroimaging data on love and passion.

They begin with the most pertinent question: “Is there any legitimate reason to associate a pathological condition (addiction) and a natural, pleasurable one [love]?”

With there being no recognized definition or diagnostic criteria for “love addiction” it is hard to posit an idea. But the bare bones of it all has some similarities to substance dependence:

“euphoria and unrestrained desire in the presence of the love object or associated stimuli (drug intoxication); negative mood, anhedonia, and sleep disturbance when separated from the love object (drug withdrawal); focussed attention on and intrusive thoughts about the love object; and maladaptive or problematic patterns of behavior (love relation) leading to clinically significant impairment or distress, with pursuit despite knowledge of adverse consequences.”

The notion of love as an addiction is described pertaining to all the usual disease addiction tropes — from a clinical description, comparing the absence of love to substance withdrawal, and — most importantly — the shift that occurs from normal to addictive state. A shift that is barely perceivable due to the simple fact that such a dependence is present in both states.

“Addiction would be defined as the stage where desire becomes a compulsive need, when suffering replaces pleasure, when one persists in the relationship despite knowledge of adverse consequences (including humiliation and shame).”

The fact that there is currently no data on the epidemiology, genetics, co-morbidity, or treatment of love addiction lead the researchers to conclude that to place some cases of “love passion” within a clinical disorder spectrum or to firmly classify it as a behavioural addiction (or to a lesser extent a disorder of impulse control) would be premature.

Addictions, particularly those to substance, short-circuit and often circumvent the natural and complex mechanisms for managing a whole range of humanistic behaviours — sensations, emotions, cognition and relationships. Add to this the fact that certain mechanisms are not well understood. Making it hard to apply it to love.

A further complication is the simple and often overlooked fact that “love” is the source of the strongest sensations, emotions, and passions known to human beings.

Originally appearing at The All Results Journal

ResearchBlogging.org

Reynaud, M., Karila, L., Blecha, L., & Benyamina, A. (2010). Is Love Passion an Addictive Disorder? The American Journal of Drug and Alcohol Abuse, 36 (5), 261-267 DOI: 10.3109/00952990.2010.495183


What had I twaught…


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