Is there any relationship between sleep and very strong Jhana?  Sleep has that characteristic of shutting off the sense doors (aside from the mind). If you take away the loose wandering and dream state and put in mindfulness and the four characteristics of Jhana, it seems like you'd get that very deep Jhana some people talk about.

For those who have experience with more intense jhana, do you think there is any relationship here (and can that be relationship be useful in finding the first jhana)?

For example, I set my mind a certain way when its time to sleep. I'm thinking perhaps doing that, but with the addition of focusing on the breath, might be a worthwhile experiment. I intend to try it either way, but interested to hear any thoughts on this subject.

Thank you. 

I've experienced lots of light jhana over the last 8 months, deep jhana just a few times.  I always spend time cultivating some jhana while in bed, just before falling asleep.  The intention and experience of jhana always seems different to me than the intention and experience of falling asleep.

Ken Folks said somewhere that he usually uses some jhana to fall asleep with.  It was a relativiely recent video interview.  Maybe this batgap interview? https://www.youtube.com/watch?v=JBXz8UVs2Pk

(Referring here to what I'll call, for the moment, "traditional jhana" – that with one-pointed absorption as per many Theravadan monastic traditions, e.g. the Visudhimagga. Not necessarily other kinds. See below (II) on a proposal for evolving some naming.)

I. Two similarities I've found (everything here to be understood as qualified by "in my expereince"):

1) Conscious, intentional methods of approaching, accessing both sleep and jhana seem similar. Taking a cue from what I've found in cultivating jhana, I've experiemented with trying to more effeciently entering sleep by noticing postural and mental tensions and systematically trying to quiet them, by way of relaxing, "letting go" of the tensions. Sometimes lying there -- "gee I've got to get to sleep here as it's late and tomorrow is a long day"-- rather than thinking about today or tomorrow, this or that; and accompaning the thoughts, hunching shoudlers and neck, stiff back, tense hands, etc. Just first noticing such things (mindfulness), and then applying whatever technique to melt the tension. Due to the total interconnection of bodily processes and sensing (conscious and unconscious) any (extranseous) tension will delay sleep onset, and take longer even afterwards to settle to deep states of sleep. This resembles checking bodily and mental 'posture', and surveying for hints of 'hindrances' on the way to access and absorptive concentration.

2) Both sleep and (this kind of) jhana are "quantum shift" sort of mental experiences – a distinct qualitative as well as quantitative (degree of  'motion', of awareness) change. With sleep, bodily and mental motion, activity ceases to be conscious. With the shift from access to absorption, the body (except for breathing, heartbeat, circulation of blood and qi) has already been more or less quieted, and the absorptive shift comes with a distinctive cessation of intentional mental motion / activity. Suddenly awareness is in the center still; the sensations of the object (or nimitta) of one-pointedness surround this center. Auditory, visual, tactile etc. stimuli still make themselves known (at least initially), but as if outside of a sort of protective shell; they don't trigger reactive engagement from the center.

BUT (3), sleep and concentrative absorption after entry are vastly dissimilar. Sleep is a virtual cessation of vivid mental awareness. Concentration is an enhancement of vivid mental awareness, and goes through subtle changes towards greater intensity, not by decisive "trying", but by intentional further letting go. Mindfulness is fully present, but without applied activity; rather a sort of passive noticing of mental qualities and somehow being able to let them change, lessen or increase.

II. 'Jhana / dhyana' , historically, means basically just doing some sort of meditation; call it simply "sitting". The term is also used to denote various specific kind of mental experience, according to various time-honored, and also various more recently discovered systems of cultivating concentration. The validity, pragmatic utility, etc. of the experiences that result is entirely a matter of individual usage and experience – no inherent good or bad, better or worse in any 'absolute' sense.

I, for one, think it would be helpful for communication, for discussion, to experiment with finding distinctive naming conventions for labelling these different systems/ experiences. So that we don't so often have people using the simple term 'jhana' to denote quite dissimilar experiences, and then 'disagreement', discussion with a lot of cognitive 'noise', if not emotive waste of energy.

Exactly how to do this, I can't specify. It probably wouldn't work for some one person or partisan group to try to specify a set of labels for their own and others' kinds of jhana experience. So maybe people, or groups can experiment with finding terms to associate with, to characterize what they mean by 'jhana'.

For instance, when Kenneth Folk or his teachers / students describe being in their sort of jhana seem to be able to verbally describe it at the same time. That it clearly not the same kind of experience as I or others have, where it's simply impossible to engage verbal action. Similarly what Leigh Brasington teaches (which I've experienced in retreat, and in reading, study) is different; and there are many other variations.

Maybe it would help to dissect out difference stages of activity, different levels, qualities, and have a multidimensional naming-space for describing jhana-s. Rather than just a set of adjectives to put before 'jhana' to distinguish these different styles – <my-name> jhana, <your-name> jhana, <his/her-name> jhana, Vism jhana, EBT ("Early Buddhist Teachings") jhana, Thai-forest jhana(s), Burmese jhana(s), American-forest (Vimalaramsi) jhana, BBSFG (Brasington+Bucknell+StuartFox+Griffiths) jhana, etc.

Enough said to indroduce this here. I've been mulling over this a while, and will offer further notes as they develop. And would, of course, look forward to considering what others may have to offer.

It's an interesting fact that sleep deprivation is supposed to aid ceremonial magick (which uses strong concentration in many cases). 

Maybe it's becouse:
"(...)sleep deprivation may result in:
- hallucinations,
- psychosis (...)"
?

https://en.wikipedia.org/wiki/Sleep_deprivation

I'd say the similarities are superficial.  Jhana is an alert one-pointed state; in sleep you just reel off into a movie/dream and deep sleep/unconsciouness.  Perhaps the tranquility (passadhi)  that one gets from jhana could be used to transition to the hypnogogic state that leads to sleep.

When doing strong samatha practice in retreat, I needed less sleep, and in bed had difficulty determing whether I was asleep, dreraming or awake. For example. I'd wake up cold, think "I'm cold even though I put that blanket on", then discover I didn't have the blanket on; the putting it on had been a dream.