Dopaminergic index	Link to schizophrenia	Strength of evidence
Drug studies	Effect of DA agonist drugs (eg amphetamine)	Induces/ worsens psychotic symptoms	+
	Effect of DA receptor antagonists (eg antipsychotics)	Reduces symptoms	++
	Effect of DA depleting drugs (eg reserpine)	Reduces symptoms	+
Peripheral markers	DA metabolites in CSF and plasma	Increased in schizophrenia	~ may depend on phase of illness and influenced by peripheral catecholamine metabolism
Ex vivo studies	Dopamine and DA metabolite levels in brain	Increased in striatum in schizophrenia	+ potentially confounded by prior antipsychotic treatment
Brain imaging studies	DA synthesis and DA release capacity, and baseline DA levels	Increased in striatum in schizophrenia	++

++=found in meta-analysis; += found in well-controlled studies; ~inconsistent findings