. 2014 Nov 10;8:361. doi: 10.3389/fnins.2014.00361

Table 1.

Summary of the effect of adolescent cannabis use on behavior in human studies.

Behavior	First cannabis use (mean age)	Mean age at test	Cannabis use	Imaging method	Evaluation	Effect	Neurobiological correlates	References
Cognition	16.8 ± 3.6	31.3 ± 7	Lifetime use	MRI/PET	–	–	Smaller whole brain	Wilson et al., 2000
			> 100 times				Smaller percent cortical gray matter
			> 100 times				Larger percent white matter volumes
	13.9 ± 1.1	21.8 ± 2.8	2.4 ± 1.6 joints a day	fMRI	Episodic memory	Encoding altered	^↑ BOLD in left parahyppocampal gyrus	Becker et al., 2010a
	14.56 ± 0.53	21.44 ± 3.57	Lifetime use	fMRI	Behavioral inhibition	^↓	^↓ activity in anterior cingulate	Gruber et al., 2012
	14.56 ± 0.53	21.44 ± 3.57	> 2500 times	fMRI	Behavioral inhibition	^↓	^↓ activity in anterior cingulate	Gruber et al., 2012
	15.7 ± 0.9	17.8 ± 1	Lifetime use	MRI	Verbal fluency	^↓	^↓ cortical thickness in right caudal middle frontal, bilateral insula and bilateral superior frontal cortices	Lopez-Larson et al., 2011
	15.7 ± 0.9	17.8 ± 1	> 100 times	MRI	Verbal fluency	^↓	^↑cortical thickness in the bilateral lingual, right superior temporal, right inferior parietal and left paracentral regions	Lopez-Larson et al., 2011
	13.1 ± 1.6	19.3 ± 0.8	5.8 joints a day	MRI	Verbal learning task	^↓	Smaller volumes in hippocampus	Ashtari et al., 2011
	14.86 ± 0.31	17.7 ± 0.94	Lifetime use	MRI	Non- planning impulsivity	^↑	^↓ right medial orbital PFC	Churchwell et al., 2010
	14.86 ± 0.31	17.7 ± 0.94	> 500 times	MRI	Non- planning impulsivity	^↑	^↓ right medial orbital PFC	Churchwell et al., 2010
	n.s.	17.7 ± 0.7	Lifetime use	ASL	Verbal learning task	^↓	^↓ CBF in the left superior and middle temporal gyri, left insula, left and right medial frontal gyrus and left supramarginal gyrus	Jacobus et al., 2012
	n.s.	17.7 ± 0.7	> 200 days	ASL	Verbal learning task	^↓		Jacobus et al., 2012
	14.1 ± 1.6	18.1 ± 0.7	Lifetime use	fMRI	Spatial Working memory	^↓	^↓ BOLD in DLPFC and occipital cortex	Schweinsburg et al., 2008
	14.1 ± 1.6	18.1 ± 0.7	> 100 times	fMRI	Spatial Working memory	^↓	^↑BOLD posterior parietal cortex	Schweinsburg et al., 2008
	16.3 ± 1.2	18.6 ± 0.8	>twice a month	–	Decision making impulsivity	^↑	–	Solowij et al., 2012
Anxiety/Depressive disorders	14.5 ± 0.5	20.1 ± 0.5	Daily use	–	Anxiety	^↑	–	Patton et al., 2002
	Follow-up study		Weekly use	–	Anxiety	^↑	–	Degenhardt et al., 2013
	<14–18>	29
	n.s.	18 ± 0.7	Lifetime use	MRI	Depressive symptoms	^↑	^↓ white matter volume	Medina et al., 2007b
	n.s.	18 ± 0.7	> 60 times	MRI	Depressive symptoms	^↑	^↓ white matter volume	Medina et al., 2007b
	Follow-up study		Lifetime ever- use	–	Depressive symptoms	^↑	–	Pedersen, 2008
	<13–17>	27
Psychosis	Follow-up study		Lifetime ever- use	–	Schizophrenic symptoms	^↑	–	Arseneault et al., 2002
	<15–18>	26
	Birth cohort study		Lifetime ever- use	–	Schizophrenic symptoms	^↑	–	Stefanis et al., 2004
	Before age of 16	18

^↓

, decrease;

^↑

, increase; MRI, magnetic resonance imaging; fMRI, functional magnetic resonance imaging; PET, positron emission tomography; ASL, arterial spin labeling; BOLD, blood oxygenation-level dependent; CBF, cerebral blood flow; PFC, prefrontal cortex; DLPFC, dorsolateral prefrontal cortex; n.s., not specified.