cannabis studies concluded that "frequent cannabis users appear to have higher levels of anxiety than non-users," and that "a considerable number of subjects developed anxiety disorders before the first symptoms of cannabis dependence." That led researchers to believe that anxiety-prone people tend to use cannabis as a self-prescribed anxiety medicine, opposing the idea that cannabis is what's causing the anxiety. MDMA (ecstasy) is a drug that also alters one's state of consciousness. The state of consciousness brought about by MDMA ingestion includes a rise in positive feelings and a reduction in negative feelings (Aldridge, D., & Fachner, J. ö. 2005). Users' emotions are increased and inhibitions lowered, often accompanied by a sensation of intimacy or connection with other people. Opioids are a class of drugs that alter consciousness. Examples of opioids include heroin, morphine, hydrocodone, and oxycodone. Opioids produce analgesia and often feelings of euphoria in users. Opioid abuse may result in decreased production of endorphins in the brain, natural pain relievers whose effects may be heightened by drugs. If one takes a large dose of opioids to compensate for the lack of natural endorphins, the result may be death. Cocaine alters one's state of consciousness. Cocaine affects the neurotransmitters that nerves use to communicate with each other. Cocaine inhibits the reuptake of norepinephrine, serotonin, dopamine, and other neurotransmitters in the synapse, resulting in an altered state of consciousness or a "high" (Aldridge, D., & Fachner, J. ö. 2005). Lysergic acid diethylamide, or LSD, activates serotonin receptors (the amine transmitter of nerve urges) in brain matter. LSD acts on certain serotonin receptors, and its effects are most prominent in the cerebral cortex, an area involved in attitude, thought, and insight, which obtains sensory signs from all parts of the body. LSD's main effects are emotional and psychological. The ingester's feelings may alter quickly through a range from fear to ecstasy. (Humphrey, N. 2001) This may cause one to experience many levels of altered consciousness. Alcohol alters consciousness by shifting levels of neurotransmitters. Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron (nerve cell) to another "target" cell (often another neuron). Neurotransmitters can cause inhibitory or excitatory effects on the "target" cell they are affecting. Alcohol increases the effect of the neurotransmitter GABA (gamma-Aminobutyric acid) in the brain. GABA causes slow actions and inaudible verbal communication that often occur in alcoholics. Alcohol also decreases the excitatory neurotransmitter