Krooninen kannabiksen käyttö on haitallista kehittyvien aivojen valkealle aineelle

kuten alla olevasta artikkelilyhennelmästä käy esille,
kannabiksen haitallisuus nuorille aivoille on jälleen kerran todistettu.

Puheet kannabiksen laillistamisesta kannattaa lykätä tuonnemmaksi,
koska uusia tuloksia erityisesti aivojen valkean aineen osalta voi löytyä lisääkin.

Andrew Zalesky,et al

Effects of long-term cannabis use on axonal fibre connectivity

Cannabis use typically begins during adolescence and early adulthood, a period when cannabinoid receptors are still abundant in
white matter pathways across the brain.

However, few studies to date have explored the impact of regular cannabis use on
white matter structure, with no previous studies examining its impact on axonal connectivity.

The aim of this study was to examine axonal fibre pathways across the brain for evidence of microstructural alterations associated with long-term cannabis use and to test whether age of regular cannabis use is associated with severity of any microstructural change. To this end,diffusion-weighted magnetic resonance imaging and brain connectivity mapping techniques were performed in 59 cannabis users with longstanding histories of heavy use and 33 matched controls.

Axonal connectivity was found to be impaired in the right fimbria of the hippocampus (fornix), splenium of the corpus callosum and commissural fibres. Radial and axial diffusivityin these pathways were associated with the age at which regular cannabis use commenced.
Our findings indicate long-term cannabis use is hazardous to the white matter of the developing brain. Delaying the age at which regular use begins may minimize the severity of microstructural impairment.

Our finding also supports mounting evidence suggesting a link between adolescent cannabis use and
schizophrenia in later life (Rais
et al., 2008; Peters et al., 2009; Dekker et al., 2010; Ho et al., 2011; James et al., 2011) as well as with evidence for greater adverse cognitive effects in adolescent cannabis users (Solowij et al., 2011a, 2012).

Our results suggest that long-term cannabis use is hazardous to white matter in the developing brain. Given the association between cannabis-related harms and age of onset of regular use, delaying use may minimize such harmful effects.

Disturbed brain connectivity in cannabis users may underlie cognitive impairment and vulnerability to psychosis, depression and anxiety disorders(Lim
et al., 2002), all of which are significant public health concerns.

White matter alterations have been associated with various functional and clinical outcomes in schizophrenia, including illness,
symptomatic and cognitive measures (Walterfang
et al., 2011), with white matter pathology underlying faulty integration of cortical–cerebellar–thalamic–cortical circuits thought to play a primary role in the observed cognitive deficits (Wexler et al., 2009).

Similar connectivity disturbances, particularly in the fimbria of the hippocampus and commissural fibres extending to the precuneus reported in this study, may underlie the memory impairment and other cognitive deficits that are observed in long-term heavy cannabis users (Solowij
et al., 2011b; Solowij and Pesa, 2012).

Brain 2012: 135; 2245–2255