cannabis and psychiatric pathology

largely studied, at times referring to themental after-effects of marijuana useand at other times discussion orresearch on this issue seemed to be fin-ished. Over the past few years, we arewitnessing a new period of intense workin this field largely due to the discoveryand analysis of the endocannabinoidsystem and the possible therapeuticapplication of cannabinoids. Researchcontinues to offer much to discover anddiscuss.

FACTORS INFLUENCING THE PSYCHOLOGICAL EFFECTS OFCANNABINOIDSRoutes of AdministrationThe psychological and behavioraleffects of marijuana vary according tothe route of administration (smoke,intravenous, or oral). When smoked, it isabsorbed in a few seconds and veryquickly reaches the brain, in a form thatis highly soluble in lipids. This quickabsorption causes most of the negativeacute effects that appear after consum-ing the drug in this way. The peak inblood appears once the cigarette hasbeen completely smoked.1-3

The oral use of THC or marijuanacauses the appearance of the maximumpeak in blood to be delayed between 1to 3 hours after an oral dose.1,4

Consequently, the beginning of the psy-chological effects is far quicker when itis consumed as a cigarette. The averageeffect of THC is estimated to be ofapproximately 20 hours.

KEY WO R D S : c a n n a b i s, p s y c h o l o g i c a lc o n s e q u e n c e s, l e g a l i z a t i o n

ABSTRACTIn the last 2 to 3 years a significant num-ber of articles about psychological con-sequences of cannabis use in humanshave been published. These articlesaddress topics such diverse topics aschronic use of cannabis and its relation-ship to schizophrenia, cognitive deterio-ration, anxiety, and the existence ofcannabis dependence. The results showthat cannabis use significantly increasesthe risk of developing any of the above-mentioned disorders. Although, theseresults require further analysis in orderto confirm or reject them.

All this is happening at a time inwhich there are an increasing number ofcannabis consumers and the medicalcommunity is trying to establish the pos-sibilities of cannabis as therapeuticagent. We should not forget the undesir-able effects when we take up a positionin the debate on legalization of cannabis.

INTRODUCTIONThe psychological effects of cannabi-noids have been known for a long time;although, the first scientific descriptionof such effects is to be found at the endof the nineteenth century. It was carriedout in 1845 by Moreau, who describedcannabis effects after having consumedthe substance himself.

Since then the subject has been

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Cannabis and PsychiatricPathology: An UpdateLuis Alfonso Núñez Domínguez, PhD

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DoseThe dose-dependant effect pattern ofcannabinoids is well known. In lowdoses cannabis acts as a sedative; in highdoses, it is a hallucinogen. Consumersfrequently have access to doses wherethe concentration is unknown.Therefore, the results produced afterusing cannabis can be different fromthose expected, for example, the appear-ance of psychotic symptoms.5

ToleranceAnother feature that can modify theeffect of marijuana is the tolerance phe-nomenon. Tolerance to its differenteffects (cardiovascular, autonomic, etc.)is rapidly acquired after repeated use ofmarijuana, both smoked and orally con-sumed. The tolerance disappears quickly,too, if cannabis use is eliminated.6

The effect of inverse tolerance hasalso been described. This means that theimpact is stronger with smaller doses,which inevitably leads to the appearanceof undesirable effects, especially thoserelated to psychological and behavioralaspects.

Experience and Use ExpectationsIt is not uncommon to see young people,in emergency rooms, who, after theirfirst contact with cannabis, show anxiousreactions, occasionally motivated by thesight of similar symptoms in friends.

The cannabis user tends to expectthe outcome to be similar to those thathe has either heard about or felt beforeduring past use.

An experienced marijuana user caneven control and adjust the dose neces-sary to obtain the effects he wishes, aswell as avoid the unwanted ones.7,8

Personality FeaturesMany of the cannabis users seek toovercome various difficulties posed intheir own lives through the use of the

substance9 A number of research workshave correlated the use of cannabis withthe appearance of schizotypal personali-ty disorders,10-12 which greatly increasethe hazard of evidencing psychoticsymptoms in high-risk individuals.

Some authors13 have found a greateruse of cannabis, in individuals who showimpulsive and anti-social traits.

Interaction with Other SubstancesMarijuana shares several metabolictraits with other substances of commonsubstances, such as alcohol, tobacco, andother therapeutic drugs, which makesinteractions inevitable. For example,THC and cannabidiol inhibit the metab-olism of substances metabolized by thehepatic system of oxidase enzymes.14-16

The absorption and clearance of othersubstances taken at the same time asmarijuana are affected (slowed down)depending on the time and sequence ofuse, and even according to previousintake. For example, the use of alcoholjust after marijuana use causes a peak inblood that is far lower than the peakthat results when it is consumed onehour before marijuana use. This is due tothe fact that THC slows down gastricemptying, as it does with alcohol absorp-tion.

REASONS FOR CANNABIS USE Through its consumption the cannabisuser seeks certain effects widely attrib-uted to this substance, such as euphoria,increase in sociability, decrease in anxi-ety caused by certain social situations(shyness, embarrassment), spontaneity,or the mere social identification with aspecific group.9 This pattern of behavior(the intake as a means of achieving cer-tain specific ends) appears to be typicalamong users of any illicit drug. In thecase of cocaine or synthetic drugs, theexpected effect is the generalized stimu-lation of physical and psychologicalfunctions, while heroine is expected to

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induce relaxation.The previous discussion refers to a

healthy population. As far as schizo-phrenics are concerned, it seems to beclear that the reasons for cannabis useare explained by the so called self-med-ication hypothesis.17 Such hypothesisassumes that in the presence of a specif-ic mental disorder, the patient turns to asubstance that will free him from thesuffering caused by his condition. Whentaking cannabis, these consumers seek toease psychological tension, aimed at thedisappearance of disturbing auditoryhallucinations, and want to overcomeapathy and aboulia, to improve socialrelations (the schizophrenic subjecttends to social isolation) as well as toovercome the depressive phase accom-panying this disorder.18,19 Initially theyseem to succeed; however, they soondevelop tolerance to the above men-tioned effects, and this leads thesepatients to a situation in which theyhave to increase their dose and frequen-cy in consumption. The result of all thisis an aggravation of their disease, withserious consequences for the subject.20

MENTAL AND BEHAVIOURALEFFECTSCommon Acute EffectsMental and behavioral effects of mari-juana include a state of well being(euphoria), a feeling of relaxation, per-ception alterations (changes in shape,color and brightness, time seems slow-er), loquacity, and an increase in socia-bility within a specific socialenvironment.21

On the other hand, other habitualresults from cannabis use include: t h edeterioration of recent memory, m o t o rcoordination (ie, impaired driving) andother psychomotor abilities; d i f f i c u l t yc o n c e n t r a t i n g, a state of stupor (being“ s t o n e d ” ) ; degradation of reactive capac-i t i e s ; decrease in mental activity; and analteration of peripheral vision.4 , 2 2 - 2 4

Very soon after repeated exposureto marijuana tolerance to a number ofsubjective and psychological resultsappears.22,25 Thus, their intensity is estab-lished, not only by the THC dose, butalso by past experiences, the user’sexpectations, the atmosphere, and thediffering sensitivity typical of each indi-vidual.26 After an average, dose, mentaleffects are easily quantified and meas-ured for a few hours (normally nolonger than 4 to 6 hours).16,23 Somestudies describe cognitive effects asremaining after 24 hours, even after asingle smoked or oral dose.22,24 Venouslevels of THC and other cannabinoidscorrelate poorly with the intensity andtype of intoxication.1,2,27

ADVERSE MENTAL EFFECTSAcute Adverse Mental Effects with Lessthan 5 Years of UseThe occasional use in sensitive, inexperi-enced individuals or persons prone toadverse effects produces brief episodesof anxiety, panic, dysphoria, depressionor mania disorders, depersonalizationand misapprehension, bizarre and self-hetero aggressive behavior, delusions (ingeneral, of a self-referential type) or hal-lucinations (more frequently visu-al).4,16,22-24,29 Depending on the mixture ofsymptoms and behavior, these manifes-tations have been called acute panicreaction, toxic delirium, acute paranoidstate or acute mania.30 The disorder mayoccasionally start acutely (shortly afterhaving finished a joint) or more slowly(1 to 2 hours) after the use of an oraldose, and usually remits completely in afew hours or a few days with no othertreatment than a relaxing environmentand the assurance, of people known tothe subject, that the symptoms havebeen caused by marijuana (a “bad trip”).In addition, marijuana clearly worsensschizophrenia.31 The reasons whycannabis is consumed by schizophrenicsand the fact that cannabis may initially



cause a partial improvement of schizo-phrenic manifestations has been dis-cussed. However, tolerance normallyappears quite soon and according to theabove-mentioned pattern. The subjectincreases the intake to ease the symp-toms, which cause an increase in the so-called positive manifestations ofschizophrenia, that is, delusions and hal-lucinations. This, in turn, leads to prob-lems in several aspects of theindividual’s life, such as social conflicts(more self-hetero aggressiveness,32)increasing number of hospital admis-sions, ceasing treatment,33 poorerresponse to psycho-pharmacologicaltreatments.34 All of these symptoms aresignals of progressive deterioration inthe disorder evolution in addition toindicating a poorer vital prognosis.20

It has also been reported thatcannabis consumption worsens the prog-nosis of bipolar disorders; cannabis caus-es an increase of the phases or cycles,showing more severe manifestations anda precocious beginning of emotionalsymptoms.35

Adverse Mental Effects After Long-term UseWhile there is a general consensus as faras the effects of marijuana are con-cerned, there is also broad disagreementconcerning outcomes after prolongeduse (more than 10 years).

Amotivational Syndrome Chronic use of marijuana has been asso-ciated with a state characterized by apa-thy and loss of motivation, together witha decline in academic results andchanges in behavior (known as “amoti-vational syndrome”).36 Very possibly, thissyndrome could only result from thekind of intoxication typical in habitualconsumers;31 however, further researchis necessary to validate this point.37,38

Cannabis Dependence?Another aspect, widely discussed untilrecently, is whether cannabis consump-tion causes dependence. Signs and symp-toms of abstinence appear in a fewhours after giving up the drug, in sub-jects included in clinical studies.39,40 Anabstinence syndrome can witnessed afteronly 5 days of low but repeated dosesfor cannabis. In double blind studieswith placebo6 or THC use, the use ofTHC reduces the symptoms or causesthem to disappear. Typical symptomsinclude: fatigue, diarrhea, insomnia, irri-tability, sweating, salivation, nausea,raised temperature, anorexia, weightloss, shivering, rebound disorder in theREM phase cycles, and subjective sleep-ing disorders. As a general rule, thesymptoms disappear within 24 to 48hours, but occasionally, sleeping disor-ders may last for weeks.

The first attempt to assess thedegree of cannabis consumers’ depend-ence has been carried out recently,through the use of a standardized ques-tionnaire, the Marijuana CravingQuestionnaire.41 The questionnaire hasproven to be a useful tool in the valida-tion of cannabis abstinence syndrome.

Cognitive Deterioration“The more consistent conductual effectsof cannabis in humans are the alterationin memory functioning.”42 It is not clearwhat happens in individuals who haveconsumed cannabis on a daily basis, with2 to 3 intakes per day, over a prolongedperiod of time. Research carried out onsuch individuals revealed a decrease inthe performance on psychological testsmeasuring cognitive capacities (ie, mem-ory).43 The controversy arises at towhether the deterioration is reversibleafter stopping the intake of cannabis.Clinical trials performed with a smallnumber of individuals have shown thatthey do recover a pre-morbid function-ing standard after withdrawal symptoms.



The effects reappear once cannabis con-sumption is re-started,44-46 although asubtle deterioration in certain cognitivecapacities seems to occur, which is non-reversible after prolonged periods ofwithdrawal.47

Cannabis PsychosisA psychotic condition with schizo-phrenic and manic symptoms, called“cannabic psychosis”, which lasts forweeks or even months, has beendescribed.48 Its existence seems to havebeen confirmed by recent studies.49 Itmay become chronic, if cannabis use ismaintained. This happens when the con-sumer continues to take the drug in thehope that the substance will rid him ofthe symptoms he is suffering from.

Most criticism directed to denyingthe existence of the cannabic psychosisare best reflected by Thornicroft (1990)and Thomas (1993)50,51 They refer to pre-vious studies that focused mainly on thewrong patients, and did not use urinaly-sis tests, standardized interviews or con-trol groups, etc. Since the 1990s, the vastmajority of published studies49,52-59 showmajor improvements in their methodol-ogy (selection of patients, use of urineanalysis, and of standardized interviews,etc.), which make the results more trust-worthy. In addition, the DSM-IVincludes and epigraph entitled,“Cannabis induced psychotic disorder”in the chapter devoted to“Schizophrenia and RelatedDisorders.”60

Nevertheless, the most recent biblio-graphic reviews61-64 continue to doubt theexistence of such a disorder, in the beliefthat it is no more than a first steptowards full schizophrenia in subjectsprone to it.50,65

Recently, a vulnerability model wasapplied to subjects who are cannabisconsumers, in an attempt to explain whya previously healthy subject, who takescannabis, continues to take it even

though he has suffered from a psychoticdisorder. Such pattern is known as “vul-nerability-stress-coping”66 and could beexplained as follows: an individual startsusing cannabis to overcome certain diffi-culties, which may be present in theirdaily activities; cannabis use increasesthe level of vulnerability towards theappearance of psychosis and, in turn,causes the appearance of a certain levelof psychosocial stress, which togetherwith cannabis use, causes schizophreniato develop. Finally, the user continues totake the drug either hoping thatcannabis will free him from the unpleas-ant feelings and perceptions caused byhis illness (delirium, hallucinations,social isolation) or to minimize theeffects that the pharmacological treat-ment.

LONG TERM EFFECTSEffects on fetus of consuming mothersAnother aspect that we cannot overlookif the effect that cannabinoids have onthe embryos of pregnant women. Theresults of research on animals show thata fetus which has been affected by theirmothers’ cannabis consumption, demon-strate important alterations in the home-ostasis of several neurotransmitters (themost studied is dopamine) and theirreceptors.67 Some of these alterationsare not reversible. A similar Canadianstudy, carried out on humans,68 demon-strated that there is a temporary alterna-tion in the appearance of the alterations:after an initial period of up to 4 to 5years, when failures in cognitive capaci-ties can be observed; an “asymptomatic”period follows, which may continue forup to 11 to 12 years, after which the cog-nitive alterations reappear once morewith additional problems including: lackof control of impulses, behavior disor-ders, and irritability.



Relationship between Cannabis andSchizophreniaIt seems quite clear that cannabis maytrigger the appearance ofschizophrenia.16,22-24,69 Linzen et al70 con-cludes that cannabis use is a risk factorin those individuals who show certain,specific, personality features or whohave a family history of psychotic disor-ders; cannabis intake could lead thesesubjects to a chronic psychosis.

After the study by Andreasson71 waswidely criticized due to several faults inmethodology, 3 new studies have beenpublished, which show how cannabisintake is an etiopathogenic factor ofschizophrenia.72-74 These studies havenot, as yet, been replicated, but themethodology used is very thorough andthe results seem conclusive.

Affective Disorders (Mania orDepression) Recent studies75 have proven thatcannabis not only worsens the evolutionand prognosis of bipolar disorders, butalso that its prolonged use may causethe appearance of such disorders or, atleast, its precocious appearance.

A study by Patton et al35 describedthe cases of young women who usedcannabis frequently and after time,showed signs of depression and anxietysymptoms, with a frequency that is 5times higher than those who do not con-sume cannabis. Arseneault et al74 alsofound similar results, with an increasenot only of the manifestations, but alsoin the depression syndrome. Rey andTennat76 share this opinion.

Gateway DrugWhereas the most recent studies havecontributed to the clarification of eachone of the previously discussed issues,this is not true concerning the questionof cannabis as a gateway drug. In 1999,the Institute of Medicine concludes thatthe data provided by the different stud-

ies carried out up to that time, were notenough to adopt a clear position; theonly clear conclusion was that in mostcases, cannabis consumption just pre-cedes the use of other drugs (excepttobacco and alcohol) but does notappear to be the cause of consumingother drugs.38 The only trustworthy pre-diction was the relation between thehigh consumption of cannabis and thepresence of a co-morbid psychiatricpathology.77

The latest studies continue to showconflicting results: Fergusson andHorwood77 conclude that cannabis mayact as a gateway drug; Beenstock andRahav79 conclude that their evidencedoes not back up the hypothesis that theuse of cannabis leads to the consump-tion of other drugs. Morral et al80 con-tribute the hypothesis that there is ageneral tendency among consumerstowards the consumption of any sub-stance, not only cannabis (Common-fac-tor model), which explains why it is notnecessary to turn to the hypothesis ofthe gateway effect of cannabis to justifyusers shifting from one substance toanother.

CONCLUSIONCannabis is the most consumed illegaldrug in the western world and it has theimage of a soft drug that is not very dan-gerous among most of its users.However, there are many potential dan-gers in its indiscriminate use, not onlymental, but also physical. Some of theeffects are irreversible (ie, cognitivedeterioration, appearance of schizophre-nia, etc.), even in cases where cannabisuse is ceased. Although it is also truethat in the vast majority of these cases,those consequences appear after pro-longed consumption.

All of this is occurring at a timewhen there is an increase both in thenumber of cannabis users and in thepercentage of THC per use, which



increases the risk of suffering undesir-able psychological effects. At the sametime, research on humans has intensi-fied, in order to assess canabinoids’ safe-ty as therapeutic agents. The adverseeffects discussed should not be over-looked when debating the pros and consof legalization of cannabis.

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