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an up- or downregulation of receptors and transporters and eventually to tolerance as well as craving when the drug is withdrawn.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

38% of Europeans affected by mental disease

Arguably, one of the most profound findings of 2011 was an epidemiological report on the mental health status of the European Union. Hans-Ulrich Wittchen and his international team of mental health experts have unraveled striking data on just how extensively disorders of the brain impact European society, and if the trend has been changing over the last three decades.   

With an initial goal to systematically assess the prevalence and burden of neurological and mental disorders in the European Union, experts from each disease category met and combined their data, only to find that it was difficult to segregate prevalence between mental and neurological disorders, due to significant overlap. However, it was possible to assess the burden of mental and neurological disease separately, when expressed as disability adjusted life years. Previous knowledge on this subject has been sparse - the World Health Organization reported an estimated 13% of global health burden to be from mental disorders. The World Mental Health Survey quotes that one in three adults suffers from a mental disorder.

Mental and Neurological Disorders Come to the Forefront: Significant Health Burden on Society

Wittchen and colleagues set out to sample all of the EU countries as well as Norway, Iceland, and Switzerland. The team combined retrospective studies, consistent reanalyses of existing epidemiological datasets and supplementary survey data from national experts to gather the best possible comprehensive dataset. 19 epidemiological panels were dispatched and at least one international expert was recruited per diagnostic group. Data was collected as far back as 1980, when the first diagnostic criteria were published on an international level (Diagnostic and Statistical Manual of Mental Disorders (DSM) and International Statistical Classification of Diseases and Related Health Problems (ICD)).
The results were startling: 38% of all Europeans are affected by disorders of the brain. Combined, mental and neurological diseases comprise Europe's largest disease burden, in terms of disability adjusted life years. The highest proportion of this burden was due to anxiety disorder, unipolar depression and insomnia.
Previously, Wittchen and colleagues had published a similar report in 2005, where the numbers were significantly more conservative, citing that 27% of the EU population are affected by mental disorder. However, this study produced a much more restrictive estimate due to age restrictions of the sample (only adults and not kids nor elderly were included), and a much more limited set of criteria for mental disorders. This time around, the team decided to get an unrestricted estimate regardless of age range or disease type.

Wittchen et al., Eur. Neuropsychopharmacol, 2011
Wittchen and Jacobi, Eur. Neuropsychopharmacol, 2005
World Health Organization, The Global Burden of Disease, 2004 Update (WHO, 2008)


By Gina Eom, Alumna MedNeuro 

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

Book Review: Bad Science

A Book by Ben Goldacre, a man who signed his dead cat up as a certified professional member of the American Association of Nutritional Consultants to prove a point.

"Let me tell you how bad things have become" begins Bad Science, before describing the Brain Gym exercises currently practiced in British schools. If you, as a budding neuroscientist (or even just as a sane individual), are concerned by the idea of children being taught that nodding their heads vigorously will make them smarter by increasing blood flow to the frontal lobes then you might want to read on. Ben Goldacre, a British doctor, is on a crusade and this book outlines his manifesto. He targets three main audiences and carries them on a crash course through modern science, mainstream media and money-making 'medical' quackery. Goldacre writes for us - scientists - as well as reaching out to people with no scientific education and imploring his 'enemies' - scare-mongering journalists and greedy nutritionists - to see reason.

Book cover of "Bad Science"

The book outlines a clear set of ideas about the advancement of public knowledge of science and Goldacre explains the obstacles he sees to these goals through a series of succinct examples of media debacles and blatant false advertising. Bad Science is the art of misinterpreting statistics, underestimating placebo effects and taking advantage of health worries and scientific ignorance in the general public to make a quick buck. Most of this is explained whilst maintaining a humorous tone - if you like gathering fun facts about the reality of recreational drug use or finding out the truth about 'Horny Goat Weed' aphrodisiacs then this is your book - but he also describes a darker side: the people who don't want to stop making money from dodgy therapies. One chapter is only included in the most recent edition of the book as Goldacre was being sued for libel by its subject, a multivitamin-pill magnate peddling lies in AIDS-striken South Africa.

Check out his TED talk!

As a population with at least basic knowledge of the procedures of evidence-based medicine, we medical neuroscientists may end up feeling a little smug as Goldacre dips into statistics and scientific reasoning. Despite this, for me at least, it served as a necessary reminder that one must always seek the full story beneath anything from a peer-reviewed academic paper to a sensationalised tabloid newspaper article. Although probably preaching to the converted, Goldacre's closing plea to scientists to make sure our work is known and not misinterpreted is sound advice. This book will make you reassess the way you think about science in the media. Please read it (or at least watch his TEDtalk).



by Ellie Rea

this article originally appeared March 2012 in Volume 5, Issue1, "Mental Health Disorders"

Why is light reflected off animal eyes at night, but not humans?

While on my way home yesterday, two eyes were staring at me out of the bushes. What is the reason for this scary phenomenon?


The phenomenon of 'eye-shine' is seen in a variety of species, and is thought to be due to the presence of an intraocular reflecting structure, the tapetum lucidum. This structure was described as early as 1854 in the Medical Lexicon by Robley Dunglison:

"TAPETUM, Ta'petry, Tape'tum choroidea. A shiny spot, on the outside of the optic nerve, in the eyes of certain animals, which is owing to the absence of the pigmentum nigrum, occasioning the reflection of a portion of the light from the membrana Ruyschiana."

Raccoons in a tree with their tapeta lucida reflecting camera flash

The Tapetum Lucidum
And he wasn't too far off back then. The tapetum lucidum is basically a biological reflector system that is a common feature in the eyes of vertebrates. Some species, usually diurnal animals (primates, squirrels, pigs), do not have this structure. Depending on the species, location and composition may differ; the tapetum lucidum can either be located within the retina or within the choriod behind the retina. The reflecting material in the tapetal cells also varies from guanine crystals (in some teleosts, reptiles) or lipid (in some teleosts, some mammals) to zinc cysteine/Riboflavin/collagen (most mammals). Therefore, not all animals eyes glow the same color, ranging from yellow, to green, to blue, and everything in between. Age and light angle can also affect the color of the eye shine. The tapetum functions like a mirror and provides the light-sensitive retinal cells with a second opportunity for photon-photoreceptor stimulation, thereby enhancing visual sensitivity at low light levels.

The Red Eye Effect
But wait a second... what about the 'human' red eye effect in pictures? Interestingly this effect rarely occurs in animals that have a tapetum lucidum; however, as we all know, it often does in humans. The cause of it is that the light flash occurs too fast for the pupil to close, allowing much of the very bright light from the flash to pass through the pupil into the eye. It then reflects off the fundus at the back of the eyeball and out through the pupil. The red to orange color which we then observe on photographs is due to the reflection of light from choroidal blood vessels.


Do you also sometimes wonder about the simple neuroscientific questions in everyday life, but don't really feel like looking them up right away? For questions like this, just mail us your question (cns-newsletter@charite.de) and Dr. Harebrained will give us his explanation!

Dunglison, Medical lexicon, p. 843., 1854
Ollivier, Vet Ophthalmol, 2004

By Veronika Lang, originally published March 2012 in Volume 5, Issue1, "Mental Health Disorders"