Drug-induced mental disorders: a common reason for concern?

Most psychoactive drugs alter our cognitive and emotional states, but does chronic use implicate a pathological change in our mental condition?

If we chronically alter transmitter pathways, adaptations will certainly take place. Adaptations are expressed during addiction in sensitization and desensitization of transmitter pathways. This leads to an up- or downregulation of receptors and transporters and eventually to tolerance as well as craving when the drug is withdrawn. These adaptations originate out of natural compensation, but leave former drug users with an imbalanced brain chemistry and an increased risk for several mental disorders. Patients with substance disorders are twice as likely to suffer from mood and anxiety disorders (National Institute on Drug Abuse). Basically, all drugs alter dopaminergic regulation and consequently, our motivation and ability to experience pleasure is changed. Several drugs also cause neurotoxicity and can therefore easily lead to permanent damage, e.g. depression after prolonged ecstasy use due to serotonergic cell death. 
Apart from emotional disturbances, the most common drug-induced illness is psychosis; with alcohol (18%), cannabis (13%) and cocaine (18%) being the most common inducers [1]. One could blame everything on 'high risk drugs', yet, for many mental disorders susceptibility genes have been found, e.g. the VAL/VAL variant of the COMT-gene in cannabis users who go on to develop schizophrenia [2]. Other factors, such as food intake, can severely affect mental outcome after chronic drug use, for example vitamin b12 deficiency in alcoholics, which can lead to several mental disorders, including psychosis and depression.
Hence, aside from chronic substance use, our environmental and genetic conditions play a decisive role in the development of long lasting drug-induced mental pathologies.
  
[1] Drake et al., Am J Psychiatry, 2011
[2] Caspi et al., Biol Psychiatry, 2005

By Anne Schwerk, PhD Alumna, AG Neuronal Regeneration and Plasticity (Dr. med. Barbara Steiner)


This article originally appeared in CNS Volume 5, Issue 1, Mental Health Disorders