Libido is a term that we commonly use to describe sexual drive or desire for sexual activity. World Health Organization states that sexual health is a state of physical, emotional, mental and social well-being in relation to sexuality, which is a reason why modern physicians recognize the importance of libido as one of the key indicators of general health and quality of life.

Throughout history, the term 'libido' had diverse meaning in the work of psychiatrists and psychoanalysts – namely Sigmund Freud who placed it on one side of his instinctual dualism, and Carl G. Jung who identified libido as a psychic energy. Today, such wide-ranging definitions are seldom used, and when talking about libido, we are mostly concentrated on sexual drive.

Evolutionary perspective of libido

Libido was conceived as ultimately biological in origin, but today it is influenced by a plethora of developmental, psychosocial and cultural factors. It is recognized as an important force in Darwinian evolution of natural selection, with an evolutionary purpose to urge species to procreate, therefore passing genetic material to subsequent generations.

A generalized sex drive is a common trait of mammalian and avian reproduction, thus many species experience fluctuations in sexual responsiveness during the estrous cycle. Women remain sexually receptive in a physiological sense throughout the menstrual cycle, with subtle cyclical variations. From an evolutionary perspective, any mechanism that can increase the frequency of intercourse during fertile days has a selective advantage by improving the chance of conception.

The human sex drive is very mental with deep roots to our cultural surroundings. Although the basic sexual drive is primarily biological in nature, specifics of attraction can be influenced on a cultural level, especially at an early age of life.

Hormonal and neurobiological basis of sexual drive

In men and women alike, libido is directly linked to androgen hormones (namely testosterone). As men have approximately 40 times as much testosterone as women, they are thought to have a more intense sexual drive; however, more aggressive behavior is demonstrated as well. Such disparity in testosterone levels also exists in other mammals, hence most species show a bias towards more pronounced sexual drive and aggression of males when compared to females.

The exact role of peptides in sexual drive and arousal is still not certain, partly because of their many roles and sites of action. Still, oxytocin – a neuropeptide also dubbed “bonding hormone” – is important in both sexual and parental behavior. Besides regulating for sexual drive, complex oxytocin neural pathways control penile erection and sexual motivation in general.

Dopamine plays a strong role in libido and motivation. This hormone and neurotransmitter is one of the key players in the human body. Steroid hormones set the stage for increased dopamine synthesis and its release during periods of enhanced sexual responding, resulting in an increased sexual drive.