Many writers have analysed Sherlock through the prism of psychology/psychiatry. I explore how brain biochemistry can provide us with an answer to why Sherlock is Sherlock.
In the process I delve into Sherlock’s possible drug habit, the effects of cocaine on the brain, the physiology of addiction, how the brain motivates us and why Sherlock, in particularly, is more prone to addiction. It puts a whole new spin on the words "I need a case."
If you ever wondered why Sherlock behaves so erratically between cases - brain biochemistry has already provided us with the answer and it has nothing to do with being mentally ill.
A Victorian Drug Binge
ACD Holmes used cocaine on a regular basis and morphine (not heroin) on occasion.
“Which is it today? Morphine or cocaine?”
“It is cocaine. A seven-per-cent solution. Would you care to try it?”
- Dr. Watson speaking to Sherlock Holmes, ‘The Sign of Four’During the Victorian era both drugs were completely legal and freely available from any pharmacist. Cocaine appeared widely in soft drinks, cigarettes and alcohol. By the mid 1880s cocaine was also available as a solution for direct injection which was ACD Holmes' preferred method of taking the drug.
Side Note - A pitiable amount: 7% solution of cocaine is much weaker than most of the injectable solutions we have in the modern day. I won't be so blithe as to say you can't get addicted on this - it is just more unlikely. However chronic use of 7% solution can still give you the changes in brain biochemistry mentioned later. I want to point out that ACD Holmes does not fulfil all the criteria addiction and therefore he is not a drug addict.
The most commonly available form of opiates in the Victorian Era was opium, a dried gum obtained from poppy seeds that contained about 12% morphine and significant amount of codeine (a potent painkiller). Opium was smoked widely throughout all levels of society although some opium dens had connotations of vice attached to them. Opiates were also available in liquid form as Laudanum, an alcoholic preparation containing 10% morphine which became a popular folk remedy for any kind of pain. Crying babies were often given Mrs Winslow’s syrup which was basically laudanum and sugar.
Heroin (the modern day solution to opiates) itself was first synthesized by CR Alder Wright in 1874. From 1898 through to 1910, diacetylmorphine was marketed under the trademark name “Heroin” as a non-addictive morphine substitute and cough suppressant.
In the Victorian era drug addiction (particularly to opium) did exist as a significant social problem but the scale was eclipsed by poverty, disease, poor sanitation and alcoholism.
Dr Watson mentions Holmes’ cocaine use as “his only vice”, which shows that by the time of ACD’s writing cocaine use was being held in ill repute by certain levels of society. In some ways it more to do with Holmes’ method of taking cocaine and his regular use. It was widely believed that “a bit” of cocaine was fairly harmless and positively useful but addiction/regular use was frowned up by the medical establishment. Although very little was understood about the science behind the addiction, doctors did realise that regular cocaine use had a negative impact on their patients' health.
A Class A Scandal in the Modern Day
In the modern era cocaine and morphine are class A drugs in the UK. This means that both possession and supply are illegal. Possession for personal use can lead to a maximum of 7 years in jail and an unlimited fine. Supplying class A drugs has a maximum penalty of life in prison and an unlimited fine.
Despite this, they are still available and used by all levels of society for recreation in the UK. Although Heroin has now become the opioid/opiate of choice instead of morphine.
Side note – medical uses of Heroin: Cocaine was historically used as a local anaesthetic for eye surgery but is now defunct. Morphine and Heroin on the other hand are frequently used, though heroin it is labelled as diamorphine. If you’ve had an operation under general anaesthetic in the UK there is a good chance that you have been given diamorphine/morphine. It is also prescribed for post operative pain (though other opoids more commonly used). Doctors emphatically refute the idea that diamorphine/morphine are very addictive. One dose is not enough to make you an addict – you need to take it for a long time and we hardly ever prescribe long term opioids unless you are terminally ill.
The police do take class A drug possession very serious but in reality comparatively few users are ever prosecuted. The police logically want to crack down on the suppliers rather than heavy handily punishing the addicts. In terms of the medical profession, we see many drug users, particularly people taking heroin overdoses, but we do not report them to the police. Firstly, because they are probably known to the police already, and secondly because it is breach of patient confidentiality.
In the UK drug users are prosecuted for crimes related to drug addiction/dealing rather than purely possessing/using the drug. Wealth in this respect protects many well-heeled individuals in society from the iniquity of arrest.
“I’m Clean – I don’t even Smoke”
Sherlock empathically claims that he is clean in ASIP – we cannot comprehensively conclude from his choice of words that he did take drugs in the past. However Lestrade knows enough about Sherlock’s past to stage a fake drugs bust. This suggests to me that Lestrade at least has good evidence that Sherlock had in the past been in possession of illegal substances. Whether or not he actually used them, we cannot say from the scant tip bits we have in BBC Sherlock.
Given the BBC version is heavily based on ACD Holmes, I imagine the writers had Sherlock down as a drug user in their back story and I am going to run with this assumption.
I do not think we can assume that just because Sherlock may have taken illegal drugs he was ever arrested, charged or convicted for drug related offences. Sherlock may or may not have been well known to the police as drug user or even drug dealer but I personally do not think he has a criminal record. Having a criminal record can seriously restrict your employability and the activities you can do. Mycroft, I am sure, would not let any of the charges stick but there will be a police record on file somewhere that Sherlock was charged even if he wasn’t convicted
Additionally I also think we can take at face value that Sherlock is indeed clean. He would be adept at hiding a drug habit but we are not given any hint of this in BBC series. However this is not say that Sherlock doesn’t occasionally possess cocaine or heroin for the purposes of experiments.
I personally don’t think Lestrade believed he was going to find anything in his fake drugs bust. Being arrested for possession of drugs is highly annoying for a consulting detective on the case and Sherlock is intelligent enough to make sure no one ever finds his stash (should he have one). Lestrade’s fake drugs bust is merely a method to punish, annoy and finally coerce Sherlock into co-operating. It appears that dragging up Sherlock’s past drug habit does aggravate the detective as does having Anderson and Sally root through his personal possessions.
Cocaine on the Brain
This next section is about what cocaine does to people’s brains in a very simplified way because there are entire textbooks on the biochemistry of the brain and I have very little time. I’ve personally never taken any of these substances and cannot tell you what it actually feels like.
Cocaine is an interesting drug because it can diffuse into the brain much easier than other psychoactive substances. There is a special filter between the blood circulating your brain and the rest of your body. It does a great job of filtering out substances that will damage your delicate neurones. Cocaine is very good at slipping the net and hence has a greater effect on the brain than heroin and many other recreational drugs.
Cocaine in the right doses cause euphoria and increased alertness/energy. This will be one reason why Sherlock likes the drug. It probably makes him feel that he is able to think quicker and more clearly. However the main reason for Sherlock's cocaine habit is all to do with feeling good.
The “high” from cocaine is due to its actions on the brain’s “reward pathway”.
Feeding Crack to Rats
Much of the knowledge we have today regarding reward and addiction is from experiments on rats. One of my professors has spent the last twenty years of his life getting rats hooked on cocaine and then imaging their brains in an attempt to solve the mystery of why we become addicted to anything.
We know that neurones communicate with each other by releasing chemicals called neurotransmitters which can either activate or depress the surrounding neurones.
In very simplified terms: there are specific areas of the brain that contain special neurones which use a chemical call dopamine to activate each other. The activation of these neurones is what makes people (and rats) very happy when they achieve something. This is the feeling Sherlock would have when he gets an interesting case and when he ultimately solves a case. Without this reward pathway - we would not be able to enjoy anything and loose all motivation.
Cocaine doesn’t technically activate these neurones it merely prolongs the time scale over which these neurones are active and helps to magnify that rewarding feeling by making sure the dopamine which is released is not broken down as quickly. Sherlock is basically getting that wonderful sense of accomplishment and joy he usually derives from cases through taking a drug.
Nicotine also has a similar effect on dopamine levels in the brain and smoking can potentiate the “high” from cocaine. I wonder perhaps if this was how Sherlock got addicted to smoking in the first place?
Just from its actions – even if cocaine wasn’t addictive you wouldn’t really want to stop using it anyway.
I don’t think Sherlock has replaced his drug addiction with crime solving as some fanfiction suggests. He was already enjoying solving the case of Carl Power’s drowning as a child. I think he turned to drugs because he could not get cases. Sherlock’s reward pathway needs constant external stimulation (more on this later). He is basically addicted to the reward of getting an interesting case and the process of solving it. Cocaine is merely a proxy he uses when he can't get high from solving crime.
We can see the vast majority of the cases that interest Sherlock are from the police. In Victorian era when the police were still an amateur force, Holmes would have been the port of call for some victims of serious crime. In the modern era the police are a professional force and much better equipped than a private investigator so Sherlock's clientele are unlikely to present with many cases that interest him.
Police procedure has also changed. As I have said before letting civilian into a police investigation is high irregular and without the correct clearance frankly illegal. Lestrade is taking a big risk letting Sherlock work on his cases (Nuclear Meltdown at the Met – Part 1). I assume before Lestrade came along Sherlock had great difficulty finding cases he enjoyed.
Dopamine Makes the World Go Round
Addiction is not an easy thing to just leave behind, you need support but you also need motivation.
I think finally being able to work with Lestrade on police cases is what actually got Sherlock to stop taking the drugs. I also personally like to imagine that Mycroft would have had a hand in this. He certainly still comes around to give Sherlock cases when all is quiet on the police front.
Despite being clean, I want to point out that Sherlock is still an addict…of dopamine*. Getting a case and then the process of solving it metaphorically lights up his reward pathway like a bonfire. He practically lives for these cases and when he’s on the case he is almost euphoric and hardly eats or sleeps. Conversely then he’s not solving crime he becomes agitated and aggressive.
Some people see these extremes as a manifestation of bipolar. I find it hard to believe that hypomanic/manic episodes would coincide so well with Sherlock’s work pattern. Instead I propose that Sherlock’s brain gives him a massive surge of dopamine in response to cases and he is addicted to this reward. When he hasn’t got a case – Sherlock goes into a kind of “withdrawal”. When cocaine addicts stop taking cocaine their dopamine levels drop which leads to motor agitation in some people. Sherlock experiences the same drop in dopamine after cases which may be the cause of Sherlock's deep agitation.
In many ways all humans live for dopamine – if there wasn’t any dopamine we’d never be motivated to do anything. However our reward pathways are activated by all achievements great and small: just having a nice slice of cake, watching a favourite TV program or meeting a friend can active our reward pathways. I personally get a boost when I read the comments on my LJ.
Sherlock, on the other hand, seems to have one very niche activity that makes his reward pathway go so wild that all other mundane stimulation pales in comparison. He has conditioned himself in such a way that solving cases has a huge effect on his reward pathway. Over time he has become dependent on that feeling of reward to the extent that he has to use drugs to try and recreate it.
Sherlock might be off the cocaine but he is still very much on the nicotine. His excessive use of patches suggests to me that he has no intention of ever relinquishing his love affair with nicotine.
*Dopamine is not the only neurotransmitter involved in reward: there are many others and this meta is long enough without a discourse on biochemistry but dopamine is the main one.
The Addictive Personality
By some quirk of nature or nurture certain individuals, like Sherlock, are much more dependent on their dopamine reward pathway than the rest of us mundane people. This phenomenon is called the “addictive personality” and it makes people more likely to become addicted to anything.
In studies of addiction using identical twins who have been raised separately, around 30% of twin pairs are both addicted to cocaine. This shows that genes play an important part in determining whether you are susceptible to addiction. The current theory is that these addictive individuals have naturally low dopamine levels. Their level of internal arousal – dopamine release in response to their own thoughts – is also very low. Thus these individuals have to seek out constant external stimuli to activate their reward pathways and give them a boost of dopamine.
Sherlock's mind is constantly active but it does not provide him with the same level of background reward that we all get. The majority of people are fully capable of keeping themselves happy and entertained without constant specific external stimuli. Sherlock needs to be working towards a converted goal in order to have the same level of contentment/satisfaction that we do just by sitting in front of the TV, eating a good meal or chatting with friends. These mundane activities simply do not produce a large enough dopamine release to keep Sherlock content.
This is my best biochemical theory of why Sherlock is Sherlock. For me, this theory pretty much explains Sherlock’s raison d'etre. He's not so much married to his work, as married to his dopamine reward pathway.