Much has been made in psychology of Freud's apparent obsession with sex as the catalyst for all of our behaviours and thoughts. A lot of criticism has been dished out for his theories and concepts such as the 'Oedipus complex', and many have found his explanations to be either overly simplistic for focussing on this one motivation, or simply distasteful.
But Freud didn't only write about sex as a motivator for human behaviour and didn't only focus on the 'libido' or 'eros instinct'. Particularly later in his career, Freud was also interested in other 'drives' that motivate our actions and thoughts, and one of the most interesting concepts he dealt with was the 'Thanatos instinct' or the 'death drive' (Freud called it 'Todestribe'). While our libido or 'sex drive' can be considered a 'life drive' for creating and perpetuating our gene pool and ensuring our own survival, the thanatos or 'death drive' describes the exact opposite: the desire to end our lives and destroy ourselves.
Understanding the Death Drive
This might sound somewhat bizarre to you, and perhaps you've already written it off as being even more deranged that his theories on our libido. In fact though, when you read into the Thanatos instinct more deeply it's something you might be more familiar with than you realise.
The death instinct you see has very little to do with suicide and much more to do with a desire to stick your head in the sand and to experience peace. The way Freud described it – in his usual vernacular – is as the desire to 'return to the womb'. This is the urge to return to a state of 'non-being' and to escape all the stresses and pressures of the daily life. But it isn't even that simple – even without stress we might find ourselves wanting to escape… ourselves… simply out of curiosity.
So perhaps you have had a bad day at work and never thought 'I just want to climb back into the womb'. But have you ever wanted to go out and get completely drunk after a bad day? Because that's essentially the same thing – it's the 'death instinct' or the desire to completely escape your own self and exist in a state other than your usual one.
Likewise you might find yourself tempted by a mind-altering drug – curious as to what you would be if you were not 'you'. Or you might cheat on your partner thinking that if it all goes to hell… well then you might get a sick fascination out of it. We all experience these feelings from time to time, and most of us are able to suppress them and get on with our lives. But in some cases they can overpower us and lead us to self-destructive behaviours.
Some psychologists after Freud have even described the sex drive – Eros – as merely a form of the death drive. Thought they might seem to be completely opposite, the similarity lies in the way you almost become 'one' with the person you have sex with. At that point you can completely lose yourself in that other person, and cease for a moment to exist as an individual. The ultimate analogy here might be those creatures that die following intercourse – now they probably need some therapy.
Of course like all of Freud's theories, the Thanatos instinct has been criticised by many subsequent psychologists and doesn't have mainstream acceptance in the community today. That said however, it certainly describes something similar to a drive we've all experienced at times: even if it isn't as prevalent as Freud might have suggested. 'Self-destructive behaviour' more specifically is a phrase that is widely accepted and dealt with.
You can read more about the death drive and Thanatos instinct from the man himself in the 1920 book Beyond the Pleasure Principle. Or if you want something a little more accessible, try the film A Dangerous Method which touches on these ideas.