US Institute of Medicine

Although euphoria is the more common reaction to smoking marijuana, adverse mood reactions can occur. Such reactions occur most frequently in inexperienced users after large doses of smoked or oral marijuana. They usually disappear within hours and respond well to reassurance and a supportive environment. Anxiety and paranoia are the most common acute adverse reactions, others include panic, depression, dysphoria, depersonalization, delusions, illusions, and hallucinations.
Source: Joy JE, Watson SJ, Benson JA, eds. Marijuana and medicine: Assessing the science base. Institute of Medicine. Washington DC: National Academy Press, 1999.
 

US Institute of Medicine

The 'high' associated with marijuana is not generally claimed to be integral to its therapeutic value. But mood enhancement, anxiety reduction, and mild sedation can be desirable qualities in medications particularly for patients suffering pain and anxiety. Thus, although the psychological effects of marijuana are merely side effects in the treatment of some symptoms, they might contribute directly to relief of other symptoms.
Source: Joy JE, Watson SJ, Benson JA, eds. Marijuana and medicine: Assessing the science base. Institute of Medicine. Washington DC: National Academy Press, 1999.
 

Giovanni Marciano and colleagues

Here we show that the endogenous cannabinoid system has a central function in extinction of aversive memories. (…) Mice were trained to associate a tone with an electric footshock (conditioning). After conditioning, animals shivered when they heard the tone. This response served as an indicator of aversive memory, and is gradually extinguished on repeated tone presentations. (...) Mice without cannabinoid-1 receptors showed strongly impaired short-term and long-term extinction of the aversive memory (...).
Overall our findings suggest that the endogenous cannabinoid system could represent a therapeutic target for the treatment of diseases associated with inappropriate retention of aversive memories or inadequate response to aversive situations, such as posttraumatic stress disorders, phobia, and certain forms of chronic pain.
Modified according to: Marsicano G, et al. The endogenous cannabinoid system controls extinction of aversive memories. Nature 2002;418(6897):530-534.
 

Pankaj Sah

Marciano and colleagues propose a new role for this endocannabinoid system - extinguishing fear-related memories in mice. The finding might have implications for treating anxiety disorders in humans.
We can form memories in several different ways, one of which is Pavlovian conditioning - the classic example being that of Pavlov's dogs, which learned to expect food whenever they heard a ringing tone. We all form these types of associations; for instance, we may associate a particular piece of music with our first love affair. But the connection need not always be pleasant. Imagine you are having a quiet walk in a park when you are threatened by an armed person. During the attack you are terrified; your heart races and your palms are sweaty. You run and escape. Later, you may find that entering the same park brings back in detail the memory of attack, right down to the sweaty palms. (...)
It has been argued that the neuronal circuitry underlying fear conditioning has similarities to that responsible for fear-related clinical conditions, such as post-traumatic stress disorder. Behavioural therapies for these conditions - including systematic desensitization and imagery therapies - share features with extinction. The finding that the endocannabinoids contribute to extinction raises the possibility that drugs that target these molecules and their receptors could be useful new treatments for anxiety disorders. Finally there is much anecdotal evidence of patients using cannabis heavily in the early stages of psychiatric illness. This has often been thought to contribute to acute illness. But it seems possible that it may instead be a form of self-medication for the sometimes extreme anxiety that these people experience.
Source: Sah P. Neurobiology: Never fear, cannabinoids are here. Nature 2002;418(6897):488-9.
 

Franjo Grotenhermen

I would like to present a case of successful cannabis use in panic attacks. A Swiss who was suffering from panic attacks recently reported me, that cannabis use was very helpful for him between the attacks. He had not used cannabis during the attack since it would be too late then.
The attacks had started about nine months ago without recognizable cause and occured nearly daily. He also suffered from nausea, loss of appetite and dizziness. He had been prescribed strong medical drugs from his doctor, which he would not like to take permanently. Five months ago he started to use cannabis, which he takes about three times a week now. The panic attacks declined in frequency and intensity. Dizziness and nausea have disappeared completely and he regained appetite. The panic attacks nearly disappeared as well.
Source: Grotenhermen F. Kann Cannabis bei einer aufkommenden Panikattacke sinnvoll eingesetzt werden? [Can cannabis be used in an arising panic attack?] Hanf-Magazin, September 2002.