Depression is a common illness with an approximate lifetime prevalence of 17 %, conferring a large burden of disease in the community, often due to inadequate treatment. Thus there is interest in the therapeutic potential of non invasive, novel forms of brain stimulation, such as transcranial direct current stimulation (tDCS). Two small studies have been published in the last two years indicating that 20 minutes of either 1 or 2mA tDCS over 5 or 10 sessions is safe, painless and well tolerated. The investigators' own pilot data (N=30) also suggests the technique has antidepressant effects and is safe (5-10 sessions of tDCS at 1 mA).

This study will extend previous findings, testing a more definitive tDCS approach (also left prefrontal anodal stimulation) with a longer treatment course (15 sessions), at 2 mA (which has been found to be safe and more effective than 1 mA in cognitive studies), and in a larger sample (N=68), using a placebo-controlled design.

It is hypothesised that active tDCS (15 sessions) will have greater efficacy than sham treatment (15 sessions) in reducing the severity of depressive symptoms in patients in an episode of major depression. A second hypothesis is that 15 sessions of tDCS will not cause any significant adverse effects or cause decline in neuropsychological functioning in comparison to a sham control.

Inclusion Criteria:

• Meets criteria for DSM-IV Major Depressive Episode

Exclusion Criteria:

• Diagnosis (as defined by DSM-IV) of: any psychotic disorder except bipolar disorder(lifetime); eating disorder (current or within the past year); obsessive compulsive disorder (lifetime); post-traumatic stress disorder (current or within the past year); mental retardation.
• History of drug or alcohol abuse or dependence (as per DSM-IV criteria) within the last 3 months (except nicotine and caffeine).
• Inadequate response to ECT in the current episode of depression.
• Subject is on regular benzodiazepine medication which it is not clinically appropriate to discontinue.
• Subject requires a rapid clinical response due to inanition, psychosis or high suicide risk.
• Neurological disorder or insult, eg recent stroke (CVA), which places subject at risk of seizure or neuronal damage with tDCS.
• Subject has metal in the cranium, skull defects, or skin lesions on scalp (cuts, abrasions, rash) at proposed electrode sites.
• Female subject who is pregnant, or of child-bearing age, sexually active and not using reliable contraception