A system and method for introducing one or more stimulating drugs and/or applying electrical stimulation to the brain to treat mood and/or anxiety disorders uses an implantable system control unit (SCU), specifically an implantable signal/pulse generator (IPG) or microstimulator with one or more electrodes in the case of electrical stimulation, and an implantable pump with one or more catheters in the case of drug infusion. In cases requiring both electrical and drug stimulation, one or more SCUs are used. Alternatively and preferably, when needed, an SCU provides both electrical stimulation and one or more stimulating drugs. In a preferred embodiment, the system is capable of open- and closed-loop operation. In closed-loop operation, at least one SCU includes a sensor, and the sensed condition is used to adjust stimulation parameters.